WO2022084844A1

WO2022084844A1 - Methods and systems for determining a time of death

Info

Publication number: WO2022084844A1
Application number: PCT/IB2021/059606
Authority: WO
Inventors: Sipho Mfolozi
Original assignee: University Of Cape Town
Priority date: 2020-10-23
Filing date: 2021-10-19
Publication date: 2022-04-28
Also published as: ZA202305527B; GB202016836D0; GB2600402A

Abstract

A body temperature measurement device includes a handle having a power supply for powering power its electronic components. A probe extends from the handle and has temperature sensors arranged along its length. The temperature sensors, as well as an orientation sensor provided in the handle, are in communication with a processor configured to communicate the temperatures and orientation sensor measurements to a remote computing device. A method for determining a time of death includes receiving temperature measurements of adjacent sites within a corpse and selecting a 3D human computational phantom corresponding to the corpse. Heat transfer from the corpse subsequent to death is simulated using the phantom and temperatures are calculated for the sites over candidate post-mortem intervals (PMIs). The calculated and measured temperatures are compared and a final PMI estimate outputted based on a candidate PMI resulting in a correlation between the calculated and measured temperatures.

Description

METHODS AND SYSTEMS FOR DETERMINING A TIME OF DEATH

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from United Kingdom patent application number 2016836.5 filed on 23 October 2020, which is incorporated by reference herein.

FIELD OF THE INVENTION

The invention disclosed herein relates to technologies and methods utilised in forensic pathology and forensic sciences and, more particularly, for use in the determination of a time of death of a body by thermometric means.

BACKGROUND TO THE INVENTION

Determination of the time of death of a corpse, or the post-mortem interval (PMI), is an important aspect of most forensic investigations. Body cooling forms the basis for one of the general methods used to estimate the time of death of a corpse.

The living human body continuously produces heat through mitochondrial oxidative phosphorylation, and it maintains its deep core temperature within a narrow temperature range using thermoregulatory mechanisms despite wide fluctuations in ambient temperature. Heat produced by the body in life is constantly lost to the surrounding environment. At death, all cellular metabolism that produces heat ceases while heat loss from the body to the surrounding environment continues as usual. The rate of heat loss from the body is influenced by multiple factors, including environmental temperature, temperature and thermophysical properties of the ground-surface, insulating characteristics of clothing items, wetness/dryness of clothing, exposure to wind, etc. When variables known to affect that rate of post-mortem body cooling are known, a body temperature taken at an unknown time after death enables estimation of the time during which the corpse would have been losing heat to the environment - the PMI.

Temperature-based methods of estimating the PMI, such as the Henssge Rectal Temperature Nomogram method, make use of a single-point deep-core temperature in refence to body temperature during life and after death. The rationale for using deep-core thermometry is that it is less influenced by temperature fluctuations of the environment. However, use of deep-core thermometry is associated with several problems. Firstly, the rate of cooling of the body immediately after death depends on the temperature distribution in the axial plane between the geometric centre of the body and the skin, rather than on the difference between the deep-core temperature and ambient temperature. Application of a single-point deep-core temperature estimate that existed at death, rather than the axial temperature distribution, leads to errors in PMI estimation calculations.

Secondly, the value of a single-point deep-core post-mortem temperature measurement depends on the depth of the measurement. This is because a large temperature gradient exists in the axial plane between the deep-core and the skin during post-mortem cooling, in which superficial body layers always have cooler temperatures than deep layers. An identical depth of temperature measurement, for example of 10cm, in a thin body with a small body radius and an obese body with a large body radius will yield different single-point deep-core temperature measurements, which in turn will yield different PMI estimation calculations. This is because 10cm for the obese body is relatively small, while the 10cm for the thin body is relatively large. Therefore, the ratio of the body radius r_body to the depth of temperature measurement r_Temp (the r_body/r_Temp ratio) should be standardised to cancel this effect. However, temperature-based methods of PMI estimation do not standardize this ratio.

Thirdly, single-point deep-core post-mortem temperature-time curve exhibits a phenomenon known as the post-mortem temperature plateau (PMTP), a variable period after death during which the measured deep-core temperature remains constant. The PMTP is problematic because it can either be absent, short or long in different corpses, yet prospective and retrospective prediction of its length for a given corpse is not possible. A single-point deep-core post-mortem temperature measurement in a corpse whose PMTP is 3 hours 54 minutes long will register the same temperature that existed before death (e.g. 37.2°C) for 3 hours 54 minutes despite the true PMI being 3 hours 54 minutes. In such a corpse, all PMIs from 0 hours 0 minutes to 3 hours 54 minutes will exhibit the same single-point deep-core post-mortem temperature measurement, which would yield the same PMI estimation calculation value. This is a source of uncertainty in the PMI estimation.

Fourthly, the position of the warmest part of the deep-core during post-mortem cooling is not identical in all bodies. Rather, it depends on the temperature, density, heat capacity and thermal conductivity (collectively, thermophysical properties) of the ground-surface on which the body rested. Ground-surfaces that cause accelerated cooling of the skin relative to cooling to air result in the warmest part of the deep-core being shifted away from that ground surface, and vice versa. A single-point deep-core temperature measurement is ‘blind’ and unable to detect the position of the warmest part of the deep-core. Empiric temperature-based methods of PMI estimation that use single-point deep-core temperature measurement do not account for thermophysical properties of the ground-surface on which the corpse rested. A single-point temperature measurement taken at the same site and depth from two identical bodies that died at the same time but rested on different ground-surfaces will yield slightly different deep-core temperature measurements, which in turn will yield different PM I estimation calculations.

The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was part of the common general knowledge in the art as at the priority date of the application.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a body temperature measurement device which includes a handle having a power supply arranged to power the electronic components of the device with a probe extending therefrom and characterised in that a plurality of temperature sensors are arranged along the length of the probe in communication with a processor in the handle and operable to read a temperature measured by each temperature sensor, with an orientation sensor provided within the handle in communication with the processor and operable to determine the orientation of either or both of the handle and the probe, and the processor configured to communicate the temperatures and orientation measurement to a remote computing device.

These features may enable the device to simultaneously measure the temperature of a plurality of adjacent sites in a body under test. The probe may be inserted substantially radially into and a body part, such as the thigh of the body under test, so that the temperature sensors (e.g. digital temperature sensors) may simultaneously measure temperatures at different radial distances from a centre or core of the body part. The orientation data may be utilised to determine the orientation at which the probe was inserted into the relevant body part, for use in mapping the measured temperature values to corresponding sites on a numerical model for simulation purposes at the remote computing device (such as a remote server).

Further features provide for the handle to include data storage accessible to the processor, the processor configured to store the temperatures measured by each temperature sensor and the orientation measured by the orientation sensor on the data storage for subsequent transmission to a remote computing device; and for the handle to include a wireless transmitter in communication with the processor with the processor being configured to transmit either or both of measured temperature values and orientation measurements to a remote computing device via the wireless transmitter.

A further feature provides for the temperature sensors to be spaced apart equally in a linear array.

These features may enable the position of a particular temperature sensor to also indicate its relative distance from other temperature sensors. This may be required for subsequent mapping of the temperature measurements to a computational phantom or numerical simulation model.

A further feature provides for the device to be connectable to a skin temperature sensor such that it is in communication with the processor, and for the processor to be operable to read a temperature measured by the skin temperature sensor.

This feature may enable an additional or auxiliary temperature sensor to be placed on the skin of the body under test, and for the read skin temperature to be transmitted to a remote computing device as an input for simulation purposes.

Further features provide for the probe to be removably secured to the handle and for the handle and probe have complementary electrical connectors arranged to interconnect the processor of the handle with the temperature sensors of the probe when the connectors are mated; for the probe to include a unique identifier readable by the processor; and for the processor to be configured to store the unique identifier of the probe. Further or alternative features provide for the probe to include a memory with the processor arranged to store a prior use indicator on the memory subsequent to the processor having obtained temperature measurements from the temperature sensors of the probe.

These features may enable and enforce single use, with the processor being able to compare a particular probe’s unique identifier with historically stored probe identifiers, and to restrict further operation using the relevant probe’s identifier if already stored by it, indicating previous use. Alternatively, the processor may digitally mark the probe as “used” after temperature measurements have been obtained from the probe. The processor may be configured to check the state of this memory and restrict further use if the memory indicates the probe as “used”.

A further feature provides for the probe to include a length identifier readable by the processor, with the length identifier indicating one or more of an overall length of the probe, a total number of temperature sensors of the probe, and a spacing of the temperature sensors of the probe.

These features may enable the device to support different lengths of probes, suited for different body sizes, or different body parts of which the temperatures are to be measured using the probe, and for the processor to automatically identify the length, number of sensors, etc. when the relevant probe is connected to the handle.

Further features provide for the handle to include one or more meteorological sensors in communication with the processor, the one or more meteorological sensors selected from the group consisting of an ambient temperature sensor, a relative air humidity sensor and an anemometer.

These features may enable the device to capture measurements of ambient conditions at the time of taking the temperature measurements of the body, with the ambient condition measurements usable as additional inputs for simulation purposes at the remote computing device of heat transfer of the body in determining a time of death.

A further feature provides for the handle to include a global navigation satellite system receiver.

These features may enable the device to determine its own position and thus the position of the body, and to transmit this location information to a remove computing device. The remote computing device may, in turn, use this information to obtain meteorological data (such as temperature and windspeed) from a weather server. The remote computing device may then use this information as inputs for simulation purposes of heat transfer of the body in determining a time of death.

Further features provide for the handle to include one or more user input component in communication with the processor; and for the one or more input components to be configured to enable input of one or more selected from the group consisting of a location of the device, anthropometric characteristics of the body, and thermophysical properties of a surface on which the body rested post-mortem.

These features may enable the user (such as a pathologist or coroner) to input physical characteristics such as the length, weight, body mass index, sex, etc. for subsequent transmission to a remote computing device as inputs for simulation purposes of heat transfer of the body in determining a time of death. Material properties may also be captured for subsequent transmission, which may be used as boundary conditions in subsequent heat transfer simulations performed at a remote computing device.

Further features provide for the handle to include one or more visual display or auditory alarm arranged to indicate a status to the user and to prompt the user for input. Further features provide for the probe to include an elongate outer sheath with a sharpened distal end, and an elongate printed circuit board housed within the outer sheath and having the temperature sensors mounted thereon, the printed circuit board providing communication paths between the processor of the handle and the temperature sensors.

Further features provide for the processor to be configured to measure a rate of change of the temperature sensors and to detect that a probe temperature has reached equilibrium with the body temperature based on the rate of change; for the processor to be configured to ignore preequilibrium temperature measurements and to store post-equilibrium temperature measurements for subsequent transmission thereof to a remote computing device and optionally indicate the reaching of a state of temperature equilibrium to a user via a display.

In accordance with a second aspect of the invention there is provided a computer-implemented method of estimating time of death which includes: receiving temperature measurements of a plurality of adjacent sites within a corpse; selecting a 3D human computational phantom corresponding to the corpse; simulating total-body temperature distribution at the time of death; simulating heat transfer or heat loss from the corpse subsequent to death using the selected 3D human computational phantom and calculating a temperature for at least a subset of the adjacent sites over one or more candidate post-mortem interval (PMI) as a result of the heat transfer or heat loss; comparing the calculated temperatures corresponding to the one or more PMI to the measured temperatures; and outputting a final PMI estimate based on a candidate PMI that results in a correlation between the calculated temperatures and the measured temperatures.

These features may enable the selection of a tested candidate PMI, or an initially guessed PMI, simulating the heat transfer for that candidate PMI, and comparing the calculated temperatures at the mapped sites with the corresponding measured values. This may take into consideration an approximation made by a forensic pathologist of the decedent’s last physical activity immediately before death from death-scene examination. Should the calculated values for the candidate PMI not correlate with the measured values, the simulation, and comparison of temperatures may then be repeated for another, different, candidate PMI.

Further features provide for the method to include iteratively selecting a longer candidate PMI if at least a subset of the calculated temperatures is higher than the corresponding measured values, repeating the simulation, and comparing the calculated temperatures for the longer candidate PMI with the corresponding measured values.

Should the simulated/calculated values for the candidate PMI be higher than the measured values, it may be inferred that the body had been deceased for longer than the candidate PMI. The simulation may then be repeated for a longer candidate PMI and the same comparison be made. Should the simulated and measured temperature values correlate (e.g. be within an acceptable margin), the candidate PMI may then be regarded as the calculated PMI. Similarly, if the calculated temperature values for a candidate PMI are lower than the measured values, it may be inferred that the candidate PMI is too long, and a shorter candidate PMI may be selected for a subsequent iteration of the simulation and comparison steps.

Alternative features provide for the method to include selecting plurality of different candidate PMIs and simultaneously simulating heat transfer for each respective candidate PMI, comparing the difference between the calculated temperatures values and corresponding measured values for each candidate PMI simulated, and outputting the final PMI estimate based on a candidate PMI that results in a correlation between the calculated temperatures and the measured temperatures.

These features may enable simultaneous simulation of multiple candidate PMIs if the computational power allows (parallelization), each in a different thread or computer core for example. This may provide a faster turnaround time than iteratively simulating using a single computer core.

Further features provide for selecting a 3D human computational phantom corresponding to the corpse to include receiving anthropometric characteristics of the body that includes at least an age, sex, and body mass index, and selecting a 3D human computational phantom from a library of available 3D human computational phantoms based on a reference body with anthropometric characteristics that best correlates with the received anthropometric characteristics.

These features may enable the selection of the most appropriate 3D human computational phantom from a library of available 3D human computational phantoms to correspond with the corpse under test. Each 3D human computational phantom may be based on a reference body having certain physical characteristics (e.g. female, 35 years of age, body mass index of 28 kg/m²). Due to their complexity, there may be a limited number of 3D human computational phantoms available and thus the closest match must be made between the available 3D human computational phantoms and the corpse under test.

Further features provide for the method to include receiving static meteorological data of a location of the corpse at a time that the received body temperature measurements were captured, the meteorological data including one or more selected from the group consisting of an ambient air temperature, a relative air humidity and a measured wind speed; and for simulating heat transfer or heat loss from the body subsequent to death to include configuring the received meteorological data as an input to the simulation.

Further features provide for the method to include receiving a location of the corpse, obtaining historic meteorological data from a weather server of the location of the corpse at a time corresponding to the one or more candidate PM Is for which the heat transfer simulation is performed, and wherein simulating heat transfer or heat loss of the corpse subsequent to death includes configuring at least a subset of obtained historic meteorological data as an input to the simulation.

Further features provide for the method to include either or both of thermophysical properties of a ground-surface on which the corpse rested post-mortem, and thermophysical properties relating to either or both of clothing or a covering of the corpse under test; and wherein simulating heat transfer or heat loss of the corpse subsequent to death includes: configuring the received thermophysical properties as an input to the simulation.

These features may enable the input of boundary conditions into the simulation so as to more precisely simulate the real-world conditions that may have affected the heat transfer of the body under test post-mortem.

Further features provide for the method to include receiving the posture of the corpse, and for simulating heat transfer or heat loss from the corpse subsequent to death using the selected 3D human computational phantom to include configuring the 3D human computational phantom of the reference corpse to assume the same or similar posture.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Figure 1 is a plan view of a body temperature measurement device in accordance with the invention including an enlarged section of a probe of the device; Figure 2 is an exploded perspective view of the device of Figure 1 ;

Figure 3 is a perspective view of the device of Figure 1 with the probe removed from a handle of the device;

Figure 4 is a perspective view showing the device in use with a probe of a different length;

Figure 5 shows the device prepared to be inserted into the thigh of a corpse;

Figure 6 is a flow diagram illustrating a method for determining time of death;

Figure 7 is a schematic of a system for determining time of death;

Figure 8 is a block diagram showing functional units of a remote computing device in the system of Figure 7; and

Figure 9 illustrates an example of a computing device in which various aspects of the disclosure may be implemented.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

Devices and systems for measuring body temperature are described below. The devices and systems may be utilised in methods for estimating a time of death. A device may include handle, which a user (such as a coroner or forensic pathologist) may use to mechanically grip the device during use, and particularly to assist in inserting a probe of the device into a corpse under test.

The handle may include a power supply, which may be required to power electronic components of the device. The above-mentioned probe may extend from the handle, particularly in use since the probe may be removably secured to the handle in certain embodiments. Since the probe part of the device (or at least an outer removable cover or sheath of the probe) comes into contact with the corpse under test, it would be considered contaminated biohazardous waste after use, and unfit for repeated use. The probe part (or at least that part intended for contact with a body under test) may therefore be disposable, or removable for disinfecting or sterilisation purposes.

The probe includes a plurality of temperature sensors arranged along its length. The length of the probe may be selected to enable it to fully traverse a target body part, such as the abdominal cavity, torso, or thigh. The spacing and total number of temperature sensors may be chosen to provide sufficient granularity in the measurement of a plurality of adjacent sites in the body within the target body part. The temperature sensors may be discrete, or individual, sensors arranged along the length of the probe, or may be integrated into a linear temperature module having a plurality of temperature sensing positions.

A processor may obtain simultaneous temperature readings of the temperature sensors. When the probe is inserted into a body part of the body under test, the temperatures will therefore be that of a number of adjacent site within the body and, more particularly, within that body part. This data is used for comparison with calculated temperatures from subsequent heat transfer simulations in which a 3D human computational phantom is used. The temperature measurements may be mapped onto the 3D human computational phantom at corresponding sites. Iterative heat transfer simulations on the 3D human computational phantoms of the (reference) body may be performed and a comparison done with the actual measurements taken in order to determine a time of death. Data from an orientation sensor in the handle may be used to assist in the mapping of the measurement sites on the numerical model.

The subsequent simulation may be performed at a remote computing device, such as a remote server, having sufficient computing capabilities. The device may therefore include a wireless transmitter (or transceiver, which includes a transmitter) to relay the measurements and metadata to the remote computing device, or to an intermediate computing device for forwarding to the remote computing device (where simulation is to occur).

Figure 1 shows an embodiment of a body temperature measurement device (10) in accordance with the invention. The device includes a handle (12) defining a housing (14) for various subcomponents of the device. A handle cover (16) for enclosing the housing (14) and the components housed therein is shown in a removed condition in Figure 1 to reveal the components housed in the housing (14). The cover (16) may be secured to the handle in its enclosed condition by means of two screws (18).

The device (10) includes a power supply housed in the handle (12) which, in the present embodiment, is a rechargeable battery (20) that powers the electronic components of the device. An elongate probe (22) extends from the handle (12) at an approximately right angle relative to the handle.

The probe (22) includes an outer sheath (24) with a sharp tip (26) at its distal end. A printed circuit board (PCB) (28) extends longitudinally within the sheath (22). Temperature sensors (30) are populated on the probe PCB (28) in a uniformly spaced linear array, which both mechanically secures the temperature sensors as well as providing electrical pathways for communication with the temperature sensors. In the present embodiment, the probe (22) has 62 temperature sensors (30) spaced 5mm from one another.

As shown more clearly in the exploded view of Figure 2, the handle (12) further includes a processor (32) that is in communication with the temperature sensors (30) and a number of further electronic components, including an orientation sensor, and wireless transmitter. In the present embodiment, the orientation sensor is a 3-axis Micro-Electro-Mechanical Systems (MEMS) accelerometer (34), and the processor (32) is arranged to obtain data representing the orientation of the handle (12) (and thus also the probe (22)) from the accelerometer. In the present embodiment, the wireless transmitter is a WIFI module (36), which includes a wireless receiver and transmitter (transceiver). The WIFI module (36) may connect to a remote computing device such as a mobile device (not shown) so as to transmit data from the processor (including temperature and orientation measurements). The mobile device may forward the data received from the device (10) to one or more further computing devices (e.g. servers with greater processing capabilities) responsible for performing heat transfer simulations as described further below.

The handle (12) further includes meteorological sensors, including an air temperature sensor (33) and an electronic hygrometer (35) for the measurement of static meteorological conditions (i.e. instantaneous meteorological measurements on site, in proximity to a corpse under test).

The handle (12) further includes data storage, presently a flash memory integrated circuit (38) in communication with the processor (32). This enables the processor (32) to store temperature measurements, orientation data, and further user inputs for example onto the flash memory (38) for later transmission to a remote computing device for further processing and simulation purposes.

The handle (12) further includes a connection (40) to enable and external or auxiliary skin temperature sensor to be connected thereto, thereby placing it in communication with the processor (32). This may enable the processor (32) to handle the skin temperature sensor as the (N+1 )^th sensor (i.e. 63^rd sensor) and include its measurements in datasets sent to a remote computing device for further processing.

In the present embodiment, the probe (22) is a disposable probe. To this end, the probe (22) is removably secured to the handle and an electrical connector (42) on the probe mates with a complementary connector of the handle when removably secured thereto so as to put the probe (and its temperature sensors (30)) in communication with the processor (32). Figure 3 shows the temperature probe (22) removed from the handle (12).

The probe (14) may include a unique identifier readable by the processor (32). For example, the probe (14) may include an EEPROM integrated circuit having a unique factory-coded serial number readable by the processor (12). This may enable the processor (12) to record the serial number and thereby mark the relevant probe (12) as “used”. This may be necessary to enforce single use to avoid cross-contamination of DNA material between corpses.

Alternatively, the probe includes a memory that the processor may program with a “used” indicator subsequent to use. This may ensure the probe will not be usable with the relevant handle (12) nor with any other such handles.

The probe may also include a length indicator. This may be required to indicate to the handle (12) (or the processor (32)) what model of probe is used. Different lengths of probes may be utilised for measurement of different body parts, or different body sizes. Figure 4 shows a probe (50) having a shorter length and having only 32 temperature sensors. The length indicator may indicate information such as the length of the probe, the total number of temperature sensors, and temperature sensor spacing, for example.

Referring back to Figure 2, the handle (12) further includes a global navigation satellite system receiver, presently a GPS receiver (44). The processor (32) may interrogate the GPS receiver (44) for its measured GPS coordinates so as to determine its own position (and thus the position of the corpse under test). These GPS coordinates may be transmitted to a remote computing device along with the temperature measurements and orientation data. The remote computing device may, in turn, use this information to obtain historic meteorological data (such as air temperature and windspeed) from a weather server to include as inputs to a simulation.

In some embodiments, the handle (12) may include meteorological sensors such as an ambient temperature sensor, a humidity sensor and an anemometer. The processor (32) may obtain meteorological data from these sensors and relay it to a remote computing device for simulation purposes.

In some embodiments, the handle (12) may include input components, for example push buttons, to enable user input (or selection) of physical characteristics of the body, material properties of a surface on which the body rested post-mortem, etc.

In use, a user may grip the device (10) by the handle (12) and insert the probe (22) into a body part of a corpse under test, which is aided by the sharp tip (26). The probe (22) is preferably inserted substantially radially into a body part, for example radially into a thigh of the corpse under test as shown in Figure 5.

The processor (32) may be configured to calculate a time derivative of temperature measurements obtained from the temperature sensors (30). This may enable the detection of temperature equilibrium of the probe (22) and the temperature sensors (30) during use. It will be appreciated that a corpse under test may have a different temperature than that of the probe (22) immediately prior to being inserted into the corpse. A settling time is required for the temperatures to reach equilibrium before temperature measurements are taken to ensure the measurements are actual readings, and not transient effects. The time to reach equilibrium may be affected by the material properties and configuration of the probe itself, and such time may be a function of the time it takes for heat transfer, or the rate of heat transfer, between the probe and the body to reduce to zero or close to zero. The handle (12) may include a display (for example an LED) or audio alarm to indicate when equilibrium is reached, and thus when measurements should be taken or captured. Alternatively, the processor (32) may be configured to automatically ignore temperature measurements taken during the settling time and to only consider temperatures measured after settling time, without alerting the user via a display or audio alarm.

The invention provides a device that may be used in a computer-implemented method (100) for estimating time of death or post-mortem interval (PMI). Figure 6 is a flow chart illustrating various steps of the method (100). The method (100) may be executed at a computing device remote to the device (10) for measuring body temperature, e.g. at a server computer with sufficient computing power for complex heat transfer and thermodynamics simulations.

A plurality of temperature measurements of adjacent sites in a corpse under test is received (102). The temperatures may have been obtained by using the device (10) for measuring body temperature described above. The device (10) may have been inserted substantially perpendicularly into a thigh of the body under test, such as to substantially traverse an entire width of the thigh. At least one of the temperature measurements may be that of a skin temperature sensor used to measure a skin temperature of the corpse under test.

A 3D human computational phantom is selected (104) from a library of available 3D human computational phantoms. The available 3D human computational phantoms may each be based on reference bodies with different physical characteristics (for example age, gender or sex, height, weight). The 3D human computational phantom may be selected (104) based on physical criteria of the corpse under test, so that the 3D human computational phantom’s physical characteristics correlate as closely as possible to that of the corpse under test. To enable selection (104) of the best correlating 3D human computational phantom from the available 3D human computational phantoms, the method may include receiving physical characteristics, or anthropometric properties, of the corpse under test, for example age, gender, height, weight (116). These characteristics may be captured using the device (10) described above or may be manually entered by an operator. The received (116) information may also include information relating to the position of the corpse, and this information may be used to manipulate joints of the 3D computational phantom so that it assumes the same posture as the corpse.

A candidate PMI is first selected (106) for which heat transfer simulation is to be performed, from which a candidate time of death is to be subsequently deduced.

A simulation (108) is then carried out to predict the total-body temperature distribution of the corpse at death at the deduced time of death using the selected 3D human computational phantom. A location of the corpse may be received (118), and historic meteorological data may also be received (120) of the location where the body was found (and thus corresponding to the received (1 18) location). This received data are applied in this total-body temperature simulation (108).

The result of the simulation (108) to predict total-body temperature distribution of the corpse at death is applied as an initial condition of a simulation to simulate (110) post-mortem heat transfer during the selected candidate PMI (106). A number of optional additional inputs or boundary conditions may be configured for the heat-transfer simulation (110). Historic meteorological data (120) of the location where the corpse was found (that is, the received (118) location) may be applied in the heat transfer simulation (1 10). Static meteorological data (122) of air temperature measurement and relative air humidity measurements measured, respectively, by an air temperature sensor (33) and an electronic hygrometer (35) inside the handle (12), are applied to this simulation (110). Thermophysical properties of the ground-surface, body coverings and clothing (124) are received (124) and applied to this simulation (110).

The result of the simulation to simulate post-mortem heat transfer (110) is interrogated at the same anatomical site on the 3D human computational phantom in which the probe (22) had been inserted into the corpse under test, e.g. the thigh. The 3-axis accelerometer data (126) measured by the accelerometer (34) is used to orientate the position where simulated temperatures are extracted and calculated for comparison. The calculated temperatures at the anatomical site in the 3D human computational phantom are compared (1 12) with the plurality of temperature measurements received (102) from measurements taken at the corpse. If the calculated temperature values do not correlate with the measured temperature values (for example if it is outside a tolerance band), a new candidate PMI is selected (106). For example, if the temperate values calculated from the simulation are higher than the measured values, it could indicate that the candidate PMI had been too short, and that the simulated heat loss had not been given enough time to result to reduce temperatures to those of the measured values. A longer candidate PMI may then be selected (106), and a further iteration of the simulations (106, 108) and comparison (112) steps performed. A number of such iterations may be performed.

If the calculated temperature values do correlate with the measured temperature values, the candidate PMI is determined and output as the final estimated PMI (1 14).

To enable yet further configuration of the simulation the method (100) may also include receiving material properties and optionally supplementary information relating to the clothing or covering of the body under test. For example, whether the body was under a blanket or shelter, and what type of clothing the body had on, if any. The method (100) may include ascribing physical characteristics, particularly heat transfer characteristics, to the clothing or covering. These material properties and further properties derived from any additional information received relating to the clothing or covering may be inputted into the simulation. It will be appreciated that these material properties, including the thermal conductivity or thermal insulation properties, may also have a substantial influence on heat transfer. Including the material properties of clothing or any covering that may have thermally insulated the body post-mortem therefore also serve to increase accuracy.

Figure 7 shows a schematic representation of a system (700) for determining time of death. The system includes a body temperature measurement device (10) as described above. The device (10) is used to take temperature measurements, obtain auxiliary information, and receive input information from a user as described above with reference to Figures 1 to 5.

Data transfer may take place between the device (10) and a mobile device (704) wirelessly. The mobile device may be any mobile computing device, including a smart phone, tablet, notebook computer, and the like. The mobile device (704) may be configured with a downloadable executable that facilitates communication and data capturing between the body temperature measurement device (10) and the mobile device (704). The connectivity of the mobile device (704) enables it to connect to a larger network, which is the internet (706) in the present embodiment.

Through the internet (706) the mobile device (704) connects to a remote computing device (710), such as a server, on which a method may be executed as described with reference to Figure 6. In some embodiments, the body temperature measurement device may be connected to the mobile device (704) via a cable. In yet further embodiments, the connectivity of the body temperature measurement device may enable it to connect to the remote computing device (710) directly (via the internet (706)), instead of using the mobile device (704) as an intermediary.

Various components may be provided for implementing the method described above with reference to Figure 6. Figure 8 is a block diagram which illustrates exemplary functional components which may be provided by a remote computing device (710) in a system (700) for determining a time of death.

The computing device (710) may include a processor (802) for executing the functions of components described below, which may be provided by hardware or by software units executing on the computing device (710). The software units may be stored in a memory component (804) and instructions may be provided to the processor (802) to carry out the functionality of the described components. In some cases, for example in a cloud computing implementation, software units arranged to manage and/or process data on behalf of the computing device (710) may be provided remotely.

The computing device (710) includes a receiver (806) arranged to receive temperature measurements of a plurality of adjacent sites within a body. A 3D computational phantom selector (808) of the computing device (710) is arranged to select a 3D computational phantom corresponding to the corpse under test.

A simulator (812) of the computing device (710) is arranged to simulate heat transfer or loss of the corpse subsequent to death using a numerical model selected by the 3D human computational phantom selector (808) and arranged to calculate a temperature of the adjacent sites over a selected candidate PMI as a result of the heat transfer or loss. The simulator (812) may select candidate PMI for which heat transfer simulation is to be performed. The candidate time of death is inferred from the candidate PMI.

The computing device (710) include a comparator (814) arranged to compare the calculated temperatures and temperature measurements received by the receiver (806). If the comparator (814) determines that temperatures do not correlate, it may instruct the simulator (810) to select a different (for example, longer) candidate PMI so that the simulation, calculation, and comparison may be iteratively repeated until the calculated and received temperature measurements correlate.

An output (814) of the computing device (710) is arranged to output a final estimated PMI based on the comparator (812) determining that a candidate PMI results in a correlation between the calculated temperatures and the measured temperatures.

The simulator (810) may alternatively be arranged to select a plurality of different candidate PMIs and simultaneously simulating heat transfer for each respective period of time.

The receiver (806) may also be arranged to receive anthropometric characteristics of the body under test, such as age, gender or sex, and body mass index, and to send the received anthropometric characteristics to the 3D human computational phantom selector (808). The 3D human computational phantom selector (808) is arranged to, in turn, base its selection of a 3D human computational phantom from a library of available 3D human computational phantoms based on a reference body with physical characteristics that best correlates with the received anthropometric characteristics.

The receiver (806) may further be arranged to receive static meteorological data of a location of the body, such as ambient temperature, a humidity and a wind speed. The receiver (806) may also be arranged to receive historic meteorological data, from a weather server for example, that prevailed during the candidate PMIs selected for simulation. The receiver (806) may forward the received data to the simulator (810) which, in turn, is arranged to apply the received meteorological data as an input to simulations.

Similarly, the receiver (806) may be arranged to receive thermophysical properties of a groundsurface on which the body rested post-mortem, as well as posture data of the body. This data may be sent to the simulator (810). The simulator (806) may use the received thermophysical properties as an input or boundary condition.

The invention therefore provides a device having a plurality of temperature sensors arranged along the length of a probe, to enable an axial thermal profile to be measured from a corpse. The axial thermal profile measured from at an unknown PMI may be compared to an axial thermal profile calculated by a computer simulation under identical simulated post-mortem cooling conditions. Application of an axial thermal profile measurement for death-time estimation addresses a number of the shortfalls previously associated with single-point deep-core postmortem temperature measurement.

Firstly, the problem of temperature-depth is eliminated because an axial thermal profile consists of temperature measurements from multiple known depths, since spacing between the plurality of temperature sensors is known. Secondly, an axial thermal profile can detect temperature changes that occur in the body during the PMTP, which would not yet be detectable to a singlepoint deep-core thermometer. Thirdly, an axial thermal profile can detect the position of the warmest part of the deep-core caused by thermophysical properties of the ground-surface, which a single-point deep-core temperature measurement cannot detect.

Figure 9 illustrates an example of a computing device (900) and its hardware components in which various aspects of the disclosure may be implemented. The computing device (900) may be embodied as any form of data processing device including a personal computing device (for example, laptop or desktop computer), a server computer (which may be self-contained, physically distributed over a number of locations), a client computer, or a communication device, such as a mobile phone (for example, cellular telephone), satellite phone, tablet computer, personal digital assistant or the like. Different embodiments of the computing device may dictate the inclusion or exclusion of various components or subsystems described below.

The computing device (900) may be suitable for storing and executing computer program code. The various participants and elements in the previously described system diagrams may use any suitable number of subsystems or components of the computing device (900) to facilitate the functions described herein. The computing device (900) may include subsystems or components interconnected via a communication infrastructure (905) (for example, a communications bus, a network, etc.). The computing device (900) may include one or more processors (910) and at least one memory component in the form of computer-readable media. The one or more processors (910) may include one or more of: CPUs, graphical processing units (GPUs), microprocessors, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs) and the like. In some configurations, a number of processors may be provided and may be arranged to carry out calculations simultaneously. In some implementations various subsystems or components of the computing device (900) may be distributed over a number of physical locations (for example, in a distributed, cluster or cloud-based computing configuration) and appropriate software units may be arranged to manage and/or process data on behalf of remote devices.

The memory components may include system memory (915), which may include read only memory (ROM) and random access memory (RAM). A basic input/output system (BIOS) may be stored in ROM. System software may be stored in the system memory (915) including operating system software. The memory components may also include secondary memory (920). The secondary memory (920) may include a fixed disk (921 ), such as a hard disk drive, and, optionally, one or more storage interfaces (922) for interfacing with storage components (923), such as removable storage components (e.g. magnetic tape, optical disk, flash memory drive, external hard drive, removable memory chip, etc.), network attached storage components (for example, NAS drives), remote storage components (for example, cloud-based storage) or the like. The computing device (900) may include an external communications interface (930) for operation of the computing device (900) in a networked environment enabling transfer of data between multiple computing devices (900) and/or the Internet. Data transferred via the external communications interface (930) may be in the form of signals, which may be electronic, electromagnetic, optical, radio, or other types of signal. The external communications interface (930) may enable communication of data between the computing device (900) and other computing devices including servers and external storage facilities. Web services may be accessible by and/or from the computing device (900) via the communications interface (930).

The external communications interface (930) may be configured for connection to wireless communication channels (for example, a cellular telephone network, wireless local area network (for example, using Wi-Fi™), satellite-phone network, Satellite Internet Network, etc.) and may include an associated wireless transfer element, such as an antenna and associated circuitry. The external communications interface (930) may include a subscriber identity module (SIM) in the form of an integrated circuit that stores an international mobile subscriber identity and the related key used to identify and authenticate a subscriber using the computing device (900). One or more subscriber identity modules may be removable from or embedded in the computing device (900).

The external communications interface (930) may further include a contactless element (950), which is typically implemented in the form of a semiconductor chip (or other data storage element) with an associated wireless transfer element, such as an antenna. The contactless element (950) may be associated with (for example, embedded within) the computing device (900) and data or control instructions transmitted via a cellular network may be applied to the contactless element (950) by means of a contactless element interface (not shown). The contactless element interface may function to permit the exchange of data and/or control instructions between computing device circuitry (and hence the cellular network) and the contactless element (950). The contactless element (950) may be capable of transferring and receiving data using a near field communications capability (or near field communications medium) typically in accordance with a standardized protocol or data transfer mechanism (for example, ISO 14443/NFC). Near field communications capability may include a short-range communications capability, such as radiofrequency identification (RFID), Bluetooth™, infra-red, or other data transfer capability that can be used to exchange data between the computing device (900) and an interrogation device. Thus, the computing device (900) may be capable of communicating and transferring data and/or control instructions via both a cellular network and near field communications capability.

The computer-readable media in the form of the various memory components may provide storage of computer-executable instructions, data structures, program modules, software units and other data. A computer program product may be provided by a computer-readable medium having stored computer-readable program code executable by the central processor (910). A computer program product may be provided by a non-transient or non-transitory computer- readable medium, or may be provided via a signal or other transient or transitory means via the communications interface (930).

Interconnection via the communication infrastructure (905) allows the one or more processors (910) to communicate with each subsystem or component and to control the execution of instructions from the memory components, as well as the exchange of information between subsystems or components. Peripherals (such as printers, scanners, cameras, or the like) and input/output (I/O) devices (such as a mouse, touchpad, keyboard, microphone, touch-sensitive display, input buttons, speakers and the like) may couple to or be integrally formed with the computing device (900) either directly or via an I/O controller (935). One or more displays (945) (which may be touch-sensitive displays) may be coupled to or integrally formed with the computing device (900) via a display or video adapter (940).

The computing device (900) may include a geographical location element (955) which is arranged to determine the geographical location of the computing device (900). The geographical location element (955) may for example be implemented by way of a global positioning system (GPS), or similar, receiver module. In some implementations the geographical location element (955) may implement an indoor positioning system, using for example communication channels such as cellular telephone or Wi-Fi™ networks and/or beacons (for example, Bluetooth™ Low Energy (BLE) beacons, iBeacons™, etc.) to determine or approximate the geographical location of the computing device (900). In some implementations, the geographical location element (955) may implement inertial navigation to track and determine the geographical location of the communication device using an initial set point and inertial measurement data.

The foregoing description has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure.

Any of the steps, operations, components or processes described herein may be performed or implemented with one or more hardware or software units, alone or in combination with other devices. In one embodiment, a software unit is implemented with a computer program product comprising a non-transient or non-transitory computer-readable medium containing computer program code, which can be executed by a processor for performing any or all of the steps, operations, or processes described. Software units or functions described in this application may be implemented as computer program code using any suitable computer language such as, for example, Java™, C++, or Perl™ using, for example, conventional or object-oriented techniques. The computer program code may be stored as a series of instructions, or commands on a non- transitory computer-readable medium, such as a random access memory (RAM), a read-only memory (ROM), a magnetic medium such as a hard-drive, or an optical medium such as a CD- ROM. Any such computer-readable medium may also reside on or within a single computational apparatus, and may be present on or within different computational apparatuses within a system or network.

Flowchart illustrations and block diagrams of methods, systems, and computer program products according to embodiments are used herein. Each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, may provide functions which may be implemented by computer readable program instructions. In some alternative implementations, the functions identified by the blocks may take place in a different order to that shown in the flowchart illustrations.

Some portions of this description describe the embodiments of the invention in terms of algorithms and symbolic representations of operations on information. These algorithmic descriptions and representations, such as accompanying flow diagrams, are commonly used by those skilled in the data processing arts to convey the substance of their work effectively to others skilled in the art. These operations, while described functionally, computationally, or logically, are understood to be implemented by computer programs or equivalent electrical circuits, microcode, or the like. The described operations may be embodied in software, firmware, hardware, or any combinations thereof.

The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention set forth in any accompanying claims.

Finally, throughout the specification and any accompanying claims, unless the context requires otherwise, the word ‘comprise’ or variations such as ‘comprises’ or ‘comprising’ will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

CLAIMS:

1 . A body temperature measurement device which includes a handle having a power supply arranged to power the electronic components of the device with a probe extending therefrom and characterised in that a plurality of temperature sensors are arranged along the length of the probe in communication with a processor in the handle and operable to read a temperature measured by each temperature sensor, with an orientation sensor provided within the handle in communication with the processor and operable to determine the orientation of either or both of the handle and the probe, and the processor configured to communicate the temperatures and orientation measurement to a remote computing device.

2. The device as claimed in claim 1 wherein the handle includes data storage accessible to the processor, the processor configured to store the temperatures measured by each temperature sensor and the orientation measured by the orientation sensor on the data storage for subsequent transmission to a remote computing device.

3. The device as claimed in claim 1 or 2 wherein the handle includes a wireless transmitter in communication with the processor with the processor being configured to transmit either or both of measured temperature values and orientation measurements to a remote computing device via the wireless transmitter.

4. The device as claimed in any one of the previous claims wherein the temperature sensors are spaced apart equally in a linear array.

5. The device as claimed in any of the previous claims wherein the device is connectable to a skin temperature sensor such that it is in communication with the processor, the processor being operable to read a temperature measured by the skin temperature sensor.

6. The device as claimed in any one of the previous claims wherein the probe is removably secured to the handle and wherein the handle and probe have complementary electrical connectors arranged to interconnect the processor of the handle with the temperature sensors of the probe when the connectors are mated.

7. The device as claimed in claim 5 or 6 wherein the probe includes a unique identifier readable by the processor, the processor being configured to store the unique identifier of the probe; and/or wherein the probe includes a memory with the processor being arranged to store a prior use indicator on the memory of the probe subsequent to the processor

22 having obtained temperature measurements from the temperature sensors of the probe. The device as claimed in claim 6 or 7 wherein the probe includes a length identifier readable by the processor, with the length identifier indicating one or more of an overall length of the probe, a total number of temperature sensors of the probe, and a spacing of the temperature sensors of the probe. The device as claimed in any one of the previous claims wherein the handle further includes one or more meteorological sensors in communication with the processor, the one or more meteorological sensors selected from the group consisting of an ambient temperature sensor, a relative air humidity sensor and an anemometer. The device as claimed in any one of the previous claims wherein the handle further includes a global navigation satellite system receiver. The device as claimed in any one of the previous claims wherein the handle further includes one or more user input component in communication with the processor, the one or more input components being configured to enable input of one or more selected from the group consisting of a location of the device, anthropometric characteristics of the body, and thermophysical properties of a surface on which the body rested post-mortem. The device as claimed in any one of the previous claims wherein the handle includes one or more visual display or auditory alarm arranged to indicate a status to the user and to prompt the user for input. The device as claimed in any one of the previous claims wherein the probe includes an elongate outer sheath with a sharpened distal end, and an elongate printed circuit board housed within the outer sheath having the temperature sensors mounted thereon, the printed circuit board providing communication paths between the processor and the temperature sensors. The device as claimed in any one of the previous claims wherein the processor is configured to measure a rate of change of the temperature sensors and to detect that a probe temperature has reached equilibrium with the body temperature based on the rate of change. The device as claimed in claim 14 wherein the processor is configured to ignore preequilibrium temperature measurements and to store post-equilibrium temperature measurements for subsequent transmission thereof to a remote computing device and optionally indicate the reaching of a state of temperature equilibrium to a user via a display. A computer-implemented method of estimating time of death which includes: receiving temperature measurements of a plurality of adjacent sites within a corpse; selecting a 3D human computational phantom corresponding to the corpse; simulating total-body temperature distribution at the time of death; simulating heat transfer or heat loss from the corpse subsequent to death using the selected 3D human computational phantom and calculating a temperature for at least a subset of the adjacent sites over one or more candidate post-mortem interval (PMI) as a result of the heat transfer or heat loss; comparing the calculated temperatures corresponding to the one or more PMI to the measured temperatures; and outputting a final PMI estimate based on a candidate PMI that results in a correlation between the calculated temperatures and the measured temperatures. The method as claimed in claim 16 including iteratively selecting a longer candidate PMI if at least a subset of the calculated temperatures is higher than the corresponding measured values, repeating the simulation, and comparing the calculated temperatures for the longer candidate PMI with the corresponding measured values. The method as claimed in claim 16 including selecting plurality of different candidate PMIs and simultaneously simulating heat transfer for each respective candidate PMI, comparing the difference between the calculated temperatures values and corresponding measured values for each candidate PMI simulated, and outputting the final PMI estimate based on a candidate PMI that results in a correlation between the calculated temperatures and the measured temperatures. The method as claimed in any one of claims 16 to 18 wherein selecting a 3D human computational phantom corresponding to the corpse includes: receiving anthropometric characteristics of the body that includes at least an age, sex, and body mass index, and selecting a 3D human computational phantom from a library of available 3D human computational phantoms based on a reference body with anthropometric characteristics that best correlates with the received anthropometric characteristics. The method as claimed in any one of claims 16 to 19 further including receiving static meteorological data of a location of the corpse at a time that the received temperature measurements were captured, the meteorological data including one or more selected from the group consisting of an ambient temperature, a relative air humidity and a wind speed, and wherein simulating heat transfer or heat loss of the corpse subsequent death includes configuring the received meteorological data as an input to the simulation. The method as claimed in any one of claims 16 to 20 further including receiving a location of the corpse, obtaining historic meteorological data from a weather server of the location of the corpse at a time corresponding to the one or more candidate PM Is for which the heat transfer simulation is performed, and wherein simulating heat transfer or heat loss of the corpse subsequent to death includes configuring at least a subset of obtained historic meteorological data as an input to the simulation. The method as claimed in any one of claims 16 to 21 further including receiving either or both of thermophysical properties of a ground-surface on which the corpse rested postmortem, and thermophysical properties relating to either or both of clothing or a covering of the corpse under test; and wherein simulating heat transfer or heat loss of the corpse subsequent to death includes: configuring the received thermophysical properties as an input to the simulation. The method as claimed in any one of claims 16 to 22 further including receiving a posture of the corpse, and wherein simulating heat transfer or heat loss from the corpse subsequent to death using the selected 3D human computational phantom includes configuring the 3D human computational phantom of the reference corpse to assume the same or similar posture.

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