- Email: [email protected]
Automatic continuous monitoring of rectal temperature using a button-type thermo data logger
Legal Medicine 8 (2006) 226–230 www.elsevier.com/locate/legalmed
Brief communication
Automatic continuous monitoring of rectal temperature using a button-type thermo data logger Jun Kanetake *, Yoshimasa Kanawaku, Masato Funayama Division of Forensic Medicine, Department of Public Health and Forensic Medicine, Tohoku University School of Medicine, 2-1 Seiryo-Machi Aoba-ku, Sendai, Miyagi 980-8575, Japan Received 27 February 2006; received in revised form 31 March 2006; accepted 3 April 2006 Available online 23 June 2006
Abstract We performed automatic continuous monitoring of rectal and ambient temperatures using button-type thermo data loggers in autopsy cases. The button-type data loggers have a battery-powered memory that can record 2048 temperature readings. The measurement intervals and other initial settings are determined by computer software, and the measurements were taken at 5-min intervals for this study. At autopsy, the data loggers were retrieved and recorded temperature graphs were produced. This study obtained three representative cases. In one case, the button-type data logger was not discharged regardless of how the body was moved after the device was inserted into the rectum. In two other cases, the cooling curves of the rectal temperature readings clearly followed changes in ambient cooling conditions. The advantages of the tested devices are their small size (diameter, 17.4 mm; thickness, 5.9 mm) and ease of insertion into the rectum, requiring no special skills. Many temperature-based algorithms to determine time of death have been developed, and as a matter of course, the temperature values must be accurate and reliable. Ensuring the validity of each temperature reading requires continuous data from an internal data logger. A button-type data logger is ideal for this purpose. q 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Time of death; Rectal temperature; Button-type thermo data logger; Autopsy case
1. Introduction Estimating the time of death is important in forensics, particularly in criminal investigations. To approximate the early postmortem period, forensic pathologists refer to lividity, rigidity, turbidity of the cornea, and other postmortem phenomena. In addition, they may also use a body temperature method based on postmortem cooling. In 1828, John Davey observed tissue temperatures of the bodies of eight British solders in Malta, though he did not estimate the time of death from his data [1]. After this, others reported the relationship between the time of death and postmortem cooling. Some attempted to create formulas to provide better results [1–5]; in practice, however, satisfactory quantification has not always been achieved. * Corresponding author. Tel.: C81 22 717 8110; fax: C81 22 717 8112. E-mail address: [email protected] (J. Kanetake).
1344-6223/$ - see front matter q 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.legalmed.2006.04.001
One problem with using postmortem cooling is that it is influenced by various factors, including ambient temperature. Another important factor is the method of measurement. In many cases, rectal temperatures are measured at some intervals at the scene of death or elsewhere, and the thermometer is inserted for each measurement. However, there is no guarantee that the thermometer tip is located at the same site in the rectum each time. In addition, if one judges time of death from just a few measurements, it is difficult to ascertain any significant changes in cooling patterns that could be affected by acute changes of circumstance. If inappropriate values are used, it is impossible to estimate the time of death despite the best of algorithms. To overcome these problems, we measured postmortem rectal temperatures using a button-type data logger, which is a device that continuously records measured temperatures.
J. Kanetake et al. / Legal Medicine 8 (2006) 226–230
In this study, we introduce the practical application of a thermo data logger taking accurate and reliable temperature measurements under postmortem conditions.
2. Materials and methods A button-type thermo data logger (SEC-CD16TB, Sanyo Electric, Osaka, Japan) (Fig. 1 and Table 1) was used to measure continuous changes in rectal temperature. This battery-powered thermometer can save 2048 consecutive data records; set in ‘endless loop’ mode, the oldest data is sequentially overwritten by new data. The initial settings, including measurement intervals and data acquisition, are set by software (Temperature and Humidity Recording System version 3.5.6, Sanyo Electric) on a computer. For this study, measurements were taken at 5-min intervals. At this setting, about 7 days of temperature data can be saved, and battery power would last about 4 years. After initialization, we distributed data loggers to each police station in Miyagi prefecture (covering a population of 2.4 million), and analyzed autopsy cases (excepting charred or decomposed bodies). For sanitary reasons, the devices were covered by a finger section from a thin latex glove (Fig. 2) and manually tucked into the rectum of the body using the top of the index finger. To record the ambient temperature, another button-type thermo data logger was set in a dedicated holder on the body’s ankle (Fig. 3). During autopsy, the data loggers were retrieved and placed in a reader connected to a computer; the data were then transferred to the computer. The transfer operation took only a few minutes, and the data were printed as a chart by the end of the autopsy. The police officer then takes the data loggers back, which can then be used for other cases without requiring re-initialization. In some cases, a handy-type thermo data-logger (TR71U, T&D Corporation, Matsumoto, Japan) was used simultaneously for comparison with the button-type
227
Table 1 Specifications of the button-type thermo data loggers Manufacturer
Sanyo Elecric, Osaka, Japan
Model Range Accuracy Resolution Intervala Modea Capacity Dimensions Weight
SEC-CD16TB K40–50 8C G1 8C 0.5 8C 1–255 min (each per min) One time or endless loop 2048 Diameter, 17.35 mm; thickness, 5.89 mm. 3.3 g
a
Interval and mode of recording is set using a computer.
detector. This type of thermometer has an elongated probe and was left continuously inserted into the rectum 10 cm beyond the anus. Ambient temperatures were measured by the device’s internal sensor. The resolution and accuracy of the device were 0.1 and 0.3 8C, respectively.
3. Results After complete insertion of a button-type data logger, no other steps were required to take measurements, and there were no other disturbances to the investigations of the sites of death. On the other hand, when using a handy-type thermo data logger, the sensor probe must be temporarily removed for picture taking, and one even fell off accidentally when the body was moved (Case 1). Three representative cases are described. In this paper, the continuous cooling graphs were recreated using Microsoft Excel 2003 in place of the original charts. 3.1. Case 1 A 49-year-old man was found dead on a road in a pool of blood. After investigation of the scene was completed, a button-type and a handy-type thermo data logger were simultaneously set in the rectum before leaving the death scene. After the body was transported to a police mortuary, external observation was performed. About 3 h later, the body was transported to the autopsy room. Fig. 4(a) and (b) show continuous monitoring charts of the button-type and handy-type data loggers, respectively. The probe of the handy-type data logger detached twice; first intentionally while taking pictures, and second accidentally when the body was moved. Following the second detachment, a drop of nearly three degrees was recorded (Fig. 4(b)). On the other hand, the button-type data logger recorded a uniform cooling pattern until the time of autopsy (Fig. 4(a)). 3.2. Case 2
Fig. 1. A button-type data logger. The resolution and accuracy are 0.5 and 1 8C, respectively.
A 53-year-old man was found dead in a room. The body was transported to a police mortuary, and a button-type data
228
J. Kanetake et al. / Legal Medicine 8 (2006) 226–230
Fig. 2. Method of wrapping a data logger in a thin latex glove for sanitary reasons. One problem that arises after insertion into the rectum is how to remove it from the anus. In autopsy cases, this is not an issue, since the rectum is dissected. If used in a non-autopsy case, a guide string should be tied to the rubber (not shown) so that it can be pulled from the anus.
logger was inserted upon completion of the external examination. After this, the body was kept in a refrigerator at the police station for 10 h and then transported for 30 min to the autopsy room. Fig. 5 shows that the rectal temperature fell rapidly after the body was placed in the refrigerator.
researchers have estimated time of death using continuous body temperature recordings [1–5]. In the 1970s, Simonsen et al. [3] measured temperatures in the brain, calf, liver, axilla, and rectum using 6-channel automatic recorders. In the 1980s, Green and Wright [4] measured rectal,
3.3. Case 3 A mother surrendered to police after strangling her 8-year-old son. The boy’s body was transported to a police mortuary and a button-type data logger was inserted into the rectum. The body was then covered by a blanket and kept in a casket for 3 h before being carried to the autopsy room and placed on a dissection table for 30 min before the autopsy began. Fig. 6 illustrates a significant fall in rectal temperature while the body was on the table.
4. Discussion Automatic continuous temperature monitoring is well established in the food industries as the HACCP (Hazard Analysis Critical Control Point) system. In forensics, some
Fig. 3. How to attach a data logger onto the body to record ambient temperatures. To avoid any temperature influence from the body surface, the holder should be suspended from one ankle of the body.
J. Kanetake et al. / Legal Medicine 8 (2006) 226–230
229
Fig. 6. Case 3: a 8-year-old boy 124 cm in height and weighing 24 kg. Rectal temperature fell rapidly after the body was placed on a dissection table. His cause of death was revealed as strangulation by ligature.
Fig. 4. Case 1: a 49-year-old man 166 cm in height and weighing 78 kg. His cause of death was revealed as blood loss due to stab wounds. (a) Records from a button-type data logger. The assailant confessed to killing the victim around 21:50. The ambient temperature was gradually rising from 7:00 p.m. and it seemed reflect arise of temperature in the daytime. (b) Records from a handy-type data logger. The probe detached twice (arrowheads) and the continuity of the cooling curve was lost after the second detachment and reinsertion. The ambient temperature showed a rapid rise immediately after re-insertion of the probe. The device has two channels, one recorded the rectal temperature through the probe and the other recorded the ambient temperature in the device. It seemed that the device was moved and contacted the body surface, and picked up the body temperature.
esophageal, and axillary temperatures automatically at 6-min intervals. Recently, Mall et al. [5] described rectal cooling temperatures from 35 bodies recorded at 5-min intervals. These reports did not indicate the shape of the devices used, but the device used by Green and Wright [4] recorded the data on a cassette tape and so was clearly larger and heavier than modern data loggers. These devices were probably limited to research use, as they would not be practical in real-life cases. Mall et al. [5] measured rectal temperatures of bodies placed in a room held at a constant ambient temperature; in practical situations, however, ambient temperatures would not be controlled. The site of the device in the rectum is important and it is said that rectal temperature must be measured at least 8 cm
Fig. 5. Case 2: a 53-year-old man 165 cm in height and weighing 49 kg. Rectal temperature fell rapidly after the body was placed in a refrigerator. His cause of death was revealed as diabetes mellitus.
deep [2]. In this study, the device was inserted into the rectum by the index finger. The average length of indexfingers of Japanese male adults was 7.1 cm [6], when one tucks the device into the rectum, it could be located in a sufficient position. One advantage of the button-type data logger is its small size and the ease of insertion into the rectum; no special skills are required. Once completely inserted, units were not discharged regardless of the movement of the body. The work required of police officers would be simple; that is, (1) wrapping a data logger in a thin rubber sleeve, (2) inserting the device into the body’s rectum, and (3) attaching a dedicated holder containing another data logger on the ankle of the body. The only important issue for the officer is to insert the data logger completely into the rectum. In Case 1, Fig. 4(b) shows how the probe of a handy-type data logger detached twice from the rectum (arrowheads) when the police moved the body. Especially following the second detachment and re-insertion, the cooling curve was clearly disrupted. The location of the re-inserted tip of the probe was probably shallower than the original position. This result indicates that when a mercury-in-glass or digital thermometer with a probe is inserted multiple times, the readings may show temperatures from different sites. Thus, discontinuous measurements may cause faulty estimations of the time of death despite the accuracy of formulas or algorithms applied. Button-type data loggers are not influenced by movements of the body and thus provide a continuous cooling curve within the limits of resolution. In Case 2, the rectal temperature fell rapidly after the body was placed in a refrigerator. Ambient temperature is likely to influence body cooling. Continuous recording of ambient temperatures from the death scene to the autopsy room was easily conducted by attaching a second data logger to an ankle of the body. In Case 3, the rectal temperature dropped rapidly after the body was placed on a dissection table. The decedent was a child, and the body’s small thermal capacity seemed to be influenced by lying uncovered on a cool object, accelerating the normal temperature loss. This reading would lead to the
230
J. Kanetake et al. / Legal Medicine 8 (2006) 226–230
estimation of an erroneous time of death, regardless of the algorithms used. Continuous recording of body temperatures would help avoid using inappropriate measurements. Of course, these changes of rectal temperatures were already well known, however, it would be important to preserve the record of rectal and ambient temperatures for reliable estimation and evidence in a court. The main problem with the button-type data loggers used in this study was their resolution of 0.5 8C. This broad resolution requires the period of measurements to be over hours so that significant changes in temperature can be obtained for analysis. This resolution would be sufficient for autopsy cases, however, because it usually takes at least several hours before an autopsy is begun due to administrative procedures. Nevertheless, it would seem straightforward to develop a data logger with a sharper resolution. Indeed, one company has already developed a button-type data logger with a resolution of 0.0625 8C [7]. Many algorithms that determine the time of death have been improved using temperature-based methods. As a matter of principle, all algorithms require their supporting data to be accurate and reliable. Henssge [2] stated that if changes in cooling conditions were known, they could be taken into account without affecting reliability or reducing accuracy. The changes in cooling conditions could be made if only the cooling chart recorded by the data logger is checked. In Japan, in almost all cases of death, one or several rectal temperature measurements are taken; at the death scene, at a police mortuary, and in the autopsy room. In addition, the persons and devices that measure these temperatures may be different each time, even for the same case; as a result, continuity of data is not maintained. To ensure that each temperature recording is valid, continuous data from an internal data logger is required. Even if a two
exponential formula is used, the extraction from these sequence data is recommended to get more reliable estimation. Button-type data loggers are suitable for this purpose, and this study demonstrates their application in practical cases.
Acknowledgements The authors thank the officers of the Miyagi Prefectural Police for their collaboration in the death investigations. Portions of this study were supported by Grants-in-Aid for Scientific Research (16590544) of the Japan Society for the Promotion of Science (JSPS).
References [1] Knight B, Nokes L. Temperature-based methods I. In: Knight B, editor. The estimation of the time since death in the early postmortem period. 2nd ed. London: Arnold; 2002. p. 3–42. [2] Henssge C. Temperature-based methods II. In: Knight B, editor. The estimation of the time since death in the early postmortem period. 2nd ed. London: Arnold; 2002. p. 43–102. [3] Simonsen J, Voigt J, Jeppesen N. Determination of the time of death by continuous post-mortem temperature measurements. Med Sci Law 1977;17:112–22. [4] Green MA, Wright JC. Postmortem interval estimation from body temperature data only. Forensic Sci Int 1985;28:35–46. [5] Mall G, Eckl M, Sinicina I, Peschel O. Temperature-based death time estimation with only partially known environmental conditions. Int J Legal Med 2005;119:185–94. [6] Kouch M, Mochimaru M. AITS Anthropometry Database of Japanese (AIST #H16PRO 287), Digital Human Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo, 2005. [7] Maxim Integrated Products, Inc. http://para.maxim-ic.com/
Brief communication
Automatic continuous monitoring of rectal temperature using a button-type thermo data logger Jun Kanetake *, Yoshimasa Kanawaku, Masato Funayama Division of Forensic Medicine, Department of Public Health and Forensic Medicine, Tohoku University School of Medicine, 2-1 Seiryo-Machi Aoba-ku, Sendai, Miyagi 980-8575, Japan Received 27 February 2006; received in revised form 31 March 2006; accepted 3 April 2006 Available online 23 June 2006
Abstract We performed automatic continuous monitoring of rectal and ambient temperatures using button-type thermo data loggers in autopsy cases. The button-type data loggers have a battery-powered memory that can record 2048 temperature readings. The measurement intervals and other initial settings are determined by computer software, and the measurements were taken at 5-min intervals for this study. At autopsy, the data loggers were retrieved and recorded temperature graphs were produced. This study obtained three representative cases. In one case, the button-type data logger was not discharged regardless of how the body was moved after the device was inserted into the rectum. In two other cases, the cooling curves of the rectal temperature readings clearly followed changes in ambient cooling conditions. The advantages of the tested devices are their small size (diameter, 17.4 mm; thickness, 5.9 mm) and ease of insertion into the rectum, requiring no special skills. Many temperature-based algorithms to determine time of death have been developed, and as a matter of course, the temperature values must be accurate and reliable. Ensuring the validity of each temperature reading requires continuous data from an internal data logger. A button-type data logger is ideal for this purpose. q 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Time of death; Rectal temperature; Button-type thermo data logger; Autopsy case
1. Introduction Estimating the time of death is important in forensics, particularly in criminal investigations. To approximate the early postmortem period, forensic pathologists refer to lividity, rigidity, turbidity of the cornea, and other postmortem phenomena. In addition, they may also use a body temperature method based on postmortem cooling. In 1828, John Davey observed tissue temperatures of the bodies of eight British solders in Malta, though he did not estimate the time of death from his data [1]. After this, others reported the relationship between the time of death and postmortem cooling. Some attempted to create formulas to provide better results [1–5]; in practice, however, satisfactory quantification has not always been achieved. * Corresponding author. Tel.: C81 22 717 8110; fax: C81 22 717 8112. E-mail address: [email protected] (J. Kanetake).
1344-6223/$ - see front matter q 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.legalmed.2006.04.001
One problem with using postmortem cooling is that it is influenced by various factors, including ambient temperature. Another important factor is the method of measurement. In many cases, rectal temperatures are measured at some intervals at the scene of death or elsewhere, and the thermometer is inserted for each measurement. However, there is no guarantee that the thermometer tip is located at the same site in the rectum each time. In addition, if one judges time of death from just a few measurements, it is difficult to ascertain any significant changes in cooling patterns that could be affected by acute changes of circumstance. If inappropriate values are used, it is impossible to estimate the time of death despite the best of algorithms. To overcome these problems, we measured postmortem rectal temperatures using a button-type data logger, which is a device that continuously records measured temperatures.
J. Kanetake et al. / Legal Medicine 8 (2006) 226–230
In this study, we introduce the practical application of a thermo data logger taking accurate and reliable temperature measurements under postmortem conditions.
2. Materials and methods A button-type thermo data logger (SEC-CD16TB, Sanyo Electric, Osaka, Japan) (Fig. 1 and Table 1) was used to measure continuous changes in rectal temperature. This battery-powered thermometer can save 2048 consecutive data records; set in ‘endless loop’ mode, the oldest data is sequentially overwritten by new data. The initial settings, including measurement intervals and data acquisition, are set by software (Temperature and Humidity Recording System version 3.5.6, Sanyo Electric) on a computer. For this study, measurements were taken at 5-min intervals. At this setting, about 7 days of temperature data can be saved, and battery power would last about 4 years. After initialization, we distributed data loggers to each police station in Miyagi prefecture (covering a population of 2.4 million), and analyzed autopsy cases (excepting charred or decomposed bodies). For sanitary reasons, the devices were covered by a finger section from a thin latex glove (Fig. 2) and manually tucked into the rectum of the body using the top of the index finger. To record the ambient temperature, another button-type thermo data logger was set in a dedicated holder on the body’s ankle (Fig. 3). During autopsy, the data loggers were retrieved and placed in a reader connected to a computer; the data were then transferred to the computer. The transfer operation took only a few minutes, and the data were printed as a chart by the end of the autopsy. The police officer then takes the data loggers back, which can then be used for other cases without requiring re-initialization. In some cases, a handy-type thermo data-logger (TR71U, T&D Corporation, Matsumoto, Japan) was used simultaneously for comparison with the button-type
227
Table 1 Specifications of the button-type thermo data loggers Manufacturer
Sanyo Elecric, Osaka, Japan
Model Range Accuracy Resolution Intervala Modea Capacity Dimensions Weight
SEC-CD16TB K40–50 8C G1 8C 0.5 8C 1–255 min (each per min) One time or endless loop 2048 Diameter, 17.35 mm; thickness, 5.89 mm. 3.3 g
a
Interval and mode of recording is set using a computer.
detector. This type of thermometer has an elongated probe and was left continuously inserted into the rectum 10 cm beyond the anus. Ambient temperatures were measured by the device’s internal sensor. The resolution and accuracy of the device were 0.1 and 0.3 8C, respectively.
3. Results After complete insertion of a button-type data logger, no other steps were required to take measurements, and there were no other disturbances to the investigations of the sites of death. On the other hand, when using a handy-type thermo data logger, the sensor probe must be temporarily removed for picture taking, and one even fell off accidentally when the body was moved (Case 1). Three representative cases are described. In this paper, the continuous cooling graphs were recreated using Microsoft Excel 2003 in place of the original charts. 3.1. Case 1 A 49-year-old man was found dead on a road in a pool of blood. After investigation of the scene was completed, a button-type and a handy-type thermo data logger were simultaneously set in the rectum before leaving the death scene. After the body was transported to a police mortuary, external observation was performed. About 3 h later, the body was transported to the autopsy room. Fig. 4(a) and (b) show continuous monitoring charts of the button-type and handy-type data loggers, respectively. The probe of the handy-type data logger detached twice; first intentionally while taking pictures, and second accidentally when the body was moved. Following the second detachment, a drop of nearly three degrees was recorded (Fig. 4(b)). On the other hand, the button-type data logger recorded a uniform cooling pattern until the time of autopsy (Fig. 4(a)). 3.2. Case 2
Fig. 1. A button-type data logger. The resolution and accuracy are 0.5 and 1 8C, respectively.
A 53-year-old man was found dead in a room. The body was transported to a police mortuary, and a button-type data
228
J. Kanetake et al. / Legal Medicine 8 (2006) 226–230
Fig. 2. Method of wrapping a data logger in a thin latex glove for sanitary reasons. One problem that arises after insertion into the rectum is how to remove it from the anus. In autopsy cases, this is not an issue, since the rectum is dissected. If used in a non-autopsy case, a guide string should be tied to the rubber (not shown) so that it can be pulled from the anus.
logger was inserted upon completion of the external examination. After this, the body was kept in a refrigerator at the police station for 10 h and then transported for 30 min to the autopsy room. Fig. 5 shows that the rectal temperature fell rapidly after the body was placed in the refrigerator.
researchers have estimated time of death using continuous body temperature recordings [1–5]. In the 1970s, Simonsen et al. [3] measured temperatures in the brain, calf, liver, axilla, and rectum using 6-channel automatic recorders. In the 1980s, Green and Wright [4] measured rectal,
3.3. Case 3 A mother surrendered to police after strangling her 8-year-old son. The boy’s body was transported to a police mortuary and a button-type data logger was inserted into the rectum. The body was then covered by a blanket and kept in a casket for 3 h before being carried to the autopsy room and placed on a dissection table for 30 min before the autopsy began. Fig. 6 illustrates a significant fall in rectal temperature while the body was on the table.
4. Discussion Automatic continuous temperature monitoring is well established in the food industries as the HACCP (Hazard Analysis Critical Control Point) system. In forensics, some
Fig. 3. How to attach a data logger onto the body to record ambient temperatures. To avoid any temperature influence from the body surface, the holder should be suspended from one ankle of the body.
J. Kanetake et al. / Legal Medicine 8 (2006) 226–230
229
Fig. 6. Case 3: a 8-year-old boy 124 cm in height and weighing 24 kg. Rectal temperature fell rapidly after the body was placed on a dissection table. His cause of death was revealed as strangulation by ligature.
Fig. 4. Case 1: a 49-year-old man 166 cm in height and weighing 78 kg. His cause of death was revealed as blood loss due to stab wounds. (a) Records from a button-type data logger. The assailant confessed to killing the victim around 21:50. The ambient temperature was gradually rising from 7:00 p.m. and it seemed reflect arise of temperature in the daytime. (b) Records from a handy-type data logger. The probe detached twice (arrowheads) and the continuity of the cooling curve was lost after the second detachment and reinsertion. The ambient temperature showed a rapid rise immediately after re-insertion of the probe. The device has two channels, one recorded the rectal temperature through the probe and the other recorded the ambient temperature in the device. It seemed that the device was moved and contacted the body surface, and picked up the body temperature.
esophageal, and axillary temperatures automatically at 6-min intervals. Recently, Mall et al. [5] described rectal cooling temperatures from 35 bodies recorded at 5-min intervals. These reports did not indicate the shape of the devices used, but the device used by Green and Wright [4] recorded the data on a cassette tape and so was clearly larger and heavier than modern data loggers. These devices were probably limited to research use, as they would not be practical in real-life cases. Mall et al. [5] measured rectal temperatures of bodies placed in a room held at a constant ambient temperature; in practical situations, however, ambient temperatures would not be controlled. The site of the device in the rectum is important and it is said that rectal temperature must be measured at least 8 cm
Fig. 5. Case 2: a 53-year-old man 165 cm in height and weighing 49 kg. Rectal temperature fell rapidly after the body was placed in a refrigerator. His cause of death was revealed as diabetes mellitus.
deep [2]. In this study, the device was inserted into the rectum by the index finger. The average length of indexfingers of Japanese male adults was 7.1 cm [6], when one tucks the device into the rectum, it could be located in a sufficient position. One advantage of the button-type data logger is its small size and the ease of insertion into the rectum; no special skills are required. Once completely inserted, units were not discharged regardless of the movement of the body. The work required of police officers would be simple; that is, (1) wrapping a data logger in a thin rubber sleeve, (2) inserting the device into the body’s rectum, and (3) attaching a dedicated holder containing another data logger on the ankle of the body. The only important issue for the officer is to insert the data logger completely into the rectum. In Case 1, Fig. 4(b) shows how the probe of a handy-type data logger detached twice from the rectum (arrowheads) when the police moved the body. Especially following the second detachment and re-insertion, the cooling curve was clearly disrupted. The location of the re-inserted tip of the probe was probably shallower than the original position. This result indicates that when a mercury-in-glass or digital thermometer with a probe is inserted multiple times, the readings may show temperatures from different sites. Thus, discontinuous measurements may cause faulty estimations of the time of death despite the accuracy of formulas or algorithms applied. Button-type data loggers are not influenced by movements of the body and thus provide a continuous cooling curve within the limits of resolution. In Case 2, the rectal temperature fell rapidly after the body was placed in a refrigerator. Ambient temperature is likely to influence body cooling. Continuous recording of ambient temperatures from the death scene to the autopsy room was easily conducted by attaching a second data logger to an ankle of the body. In Case 3, the rectal temperature dropped rapidly after the body was placed on a dissection table. The decedent was a child, and the body’s small thermal capacity seemed to be influenced by lying uncovered on a cool object, accelerating the normal temperature loss. This reading would lead to the
230
J. Kanetake et al. / Legal Medicine 8 (2006) 226–230
estimation of an erroneous time of death, regardless of the algorithms used. Continuous recording of body temperatures would help avoid using inappropriate measurements. Of course, these changes of rectal temperatures were already well known, however, it would be important to preserve the record of rectal and ambient temperatures for reliable estimation and evidence in a court. The main problem with the button-type data loggers used in this study was their resolution of 0.5 8C. This broad resolution requires the period of measurements to be over hours so that significant changes in temperature can be obtained for analysis. This resolution would be sufficient for autopsy cases, however, because it usually takes at least several hours before an autopsy is begun due to administrative procedures. Nevertheless, it would seem straightforward to develop a data logger with a sharper resolution. Indeed, one company has already developed a button-type data logger with a resolution of 0.0625 8C [7]. Many algorithms that determine the time of death have been improved using temperature-based methods. As a matter of principle, all algorithms require their supporting data to be accurate and reliable. Henssge [2] stated that if changes in cooling conditions were known, they could be taken into account without affecting reliability or reducing accuracy. The changes in cooling conditions could be made if only the cooling chart recorded by the data logger is checked. In Japan, in almost all cases of death, one or several rectal temperature measurements are taken; at the death scene, at a police mortuary, and in the autopsy room. In addition, the persons and devices that measure these temperatures may be different each time, even for the same case; as a result, continuity of data is not maintained. To ensure that each temperature recording is valid, continuous data from an internal data logger is required. Even if a two
exponential formula is used, the extraction from these sequence data is recommended to get more reliable estimation. Button-type data loggers are suitable for this purpose, and this study demonstrates their application in practical cases.
Acknowledgements The authors thank the officers of the Miyagi Prefectural Police for their collaboration in the death investigations. Portions of this study were supported by Grants-in-Aid for Scientific Research (16590544) of the Japan Society for the Promotion of Science (JSPS).
References [1] Knight B, Nokes L. Temperature-based methods I. In: Knight B, editor. The estimation of the time since death in the early postmortem period. 2nd ed. London: Arnold; 2002. p. 3–42. [2] Henssge C. Temperature-based methods II. In: Knight B, editor. The estimation of the time since death in the early postmortem period. 2nd ed. London: Arnold; 2002. p. 43–102. [3] Simonsen J, Voigt J, Jeppesen N. Determination of the time of death by continuous post-mortem temperature measurements. Med Sci Law 1977;17:112–22. [4] Green MA, Wright JC. Postmortem interval estimation from body temperature data only. Forensic Sci Int 1985;28:35–46. [5] Mall G, Eckl M, Sinicina I, Peschel O. Temperature-based death time estimation with only partially known environmental conditions. Int J Legal Med 2005;119:185–94. [6] Kouch M, Mochimaru M. AITS Anthropometry Database of Japanese (AIST #H16PRO 287), Digital Human Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo, 2005. [7] Maxim Integrated Products, Inc. http://para.maxim-ic.com/