Chiba Prefectural Police

In Accidents that the car collided with the person lying on the road, the case fatality rate and hit-and-run rate were high, so the recognition of the location where the victim could be found was often the issue. There was also the cognitive error due to the driver’s belief that a person could not lie on the road. There were many researches on the driver’s visibility in pedestrian accidents, whereas there were few studies conducted on those of the person lying on the road. In this research, we conducted the driving experiment to examine whether the visually recognizable distance of the person lying on the road in night driving changed depending on the speed. There were no significant difference of the visually recognizable distance between slow speed, 40 km/h, and 60 km/h.

In the case of a fire incident such as arson, the combustion experiment that reconstructed the fire scene will be conducted to clarify the facts. However, various problems such as construction costs and securing an experimental environment must be dealt with. Therefore, the purpose of this study is to utilize fire simulation for the investigation of fire incidents. In this study, combustion experiments and FDS (Fire Dynamics Simulator) simulations assuming gasoline arson in the kitchen, which have not been reported so far, were conducted and compared. Next, the observation of fire damage using the accumulated heat-flux was evaluated by a newly developed analysis tool for visual evaluation. The simulation results such as burning behavior, temperature changes, and the burned away phenomenon of the door showed good agreement with those experimental results. Burning behavior in the kitchen, that couldn't be observed in the combustion experiment were grasped in detail in the simulation. Furthermore, the relationship between the fire source and the fire damage on the floor, which couldn't be explained only by the observation results after extinguishing the fire, could be reasonably explained by the visual evaluation of burning behavior and the accumulated heat-flux in the kitchen by using the simulation. Therefore, the fire simulation was shown to be an effective tool for analyzing fire phenomena.

The Autobiographical Implicit Association Test (aIAT) is a reaction time-based methodology to assess one's recognition of the truth value of propositions about an autobiographical episode. This study introduced pupillometry to examine its utility as an additional measure of aIAT. Participants blindly chose one of two cards and memorized it. They then underwent the aIAT to assess the cards they chose. The pupil diameter was larger in the block in which sentences related to the chosen card shared the same response key with sentences describing false events than the block in which sentences related to the chosen card shared the same response key with true-event sentences. Although preliminary, pupil measurement also yielded high efficiency in discriminating the chosen card. These results indicate that pupillometry can be used as a measure of aIAT.

Forensic biologists are increasingly likely to identify an individual using three-dimensional imaging equipment. Existing equipment requires taking the subjects to the place where the equipment is located. In recent years, a non-contact, hand-held three-dimensional color scanner has been developed that is compact and lightweight. Therefore, we already use it for facial recognition and cranio-facial superimposition. The three-dimensional scanner reconstructed skull images precisely, and the anthropological measurements obtained from the images were comparable to those obtained from actual skulls (the differences in measurements were less than 1mm). Furthermore, the skull images produced by the scanner corresponded with high accuracy to the three-dimensional images reconstructed using computed tomography (concordance rates were approximately 95%) and to the two-dimensional facial photographs of the same person (the differences were less than the standard value 2.5mm for the reciprocal point-to-point matching). In addition to the skull images, the three-dimensional scanner precisely reconstructed facial images of living people. The three-dimensional facial images approximately corresponded to the two-dimensional facial photographs of the same people taken from both the vertical direction and from a bird's-eye view (the difference were less than the standard values, 0.9mm for the outline matching and 2.5mm for the reciprocal point-to-point matching). In conclusion, the current study confirmed that the non-contact, hand-held three-dimensional color scanner can provide forensic biologists with precise three-dimensional images of both skulls and living people's faces and that the images are of sufficiently good quality to be put to practical use as the quality of conventional stationary type.

In order to estimate type and trajectory of the fired bullet from the analysis of the ricochet mark, we carried out the gunfire test against the inclined target. 1.2 mm thin steel plates were used as intermediate targets in this study. The following are types of cartridges which were used: 25 AUTO., 32 AUTO., 7.62 mm Tokarev, 380 AUTO., 38 SPL. (FMC), 38 SPL. (LRN), 9 mm Luger and 45 AUTO.. The target was put in a wooden frame. The angle of incidence was changed by rotating the wooden frame. We could classify the deformation morphology on the thin steel plate into 4 patterns: Ricochet mark without the crack (Type 1), Ricochet mark with the small crack (Type 2), Ricochet mark with the large crack (Type 3), Penetration (Type 4). Metal from the bullet surface was left on the surface of the target. It was thought that the crack in the edge of the ricochet mark (Type 2 or 3) was caused by the friction arising from the rifling rotation of the fired bullet. The length of the ricochet mark in the longitudinal direction L increases with increase of the kinetic energy of the bullet E. The value of L was relative to the kinetic energy resolved into the horizontal component of the velocity Ecos2θi (θi: the angle of incidence). Except for 380 AUTO. and 38 SPL., the value of L was almost independent of E and Ecos2θi respectively. The ratio of the angle of ricochet θr to the angle of incidence θi was around 1 to 2. Therefore, caliber and type of a fired bullet and the trajectory can be determined from the analysis of the ricochet mark and the contour when the bullet is fired into a 1.2 mm thin steel plate.

Postmortem computed tomography (CT) images can show internal findings related to the cause of death, and it can be a useful method for forensic diagnosis. In this study, we scanned a ready-made box by helical CT on 2-mm slices in a mobile CT scanner and measured each side of the box to assess whether reconstructed images are useful for superimposition. The mean difference between the actual measurements and the measurements on the three-dimensional (3D) reconstructed images (3D-CT images) is 0.9 mm; we regarded it as having no effect on reconstruction for the superimposition method. Furthermore, we could get 3D-CT images of the skull, which were consistent with the actual skull, indicating that CT images can be applied to superimposition for identification. This study suggested that postmortem CT images can be applied as superimpositions for unidentified cases, and thinner slices or cone beam CT can be a more precise tool.

With the spread of hair coloring, the number of cases where dyed hairs are examined as evidential samples is on the increase. In forensic casework, hair color observed with the naked eye and light microscope is an important characteristic for morphological examination, while the color of dyed hair is considered of little importance and sometimes is excluded from examination because it no longer has its original color. It is experientially recognized that peculiar morphology is often observed in the cross section of dyed hairs. However, making cross sections of hair is so laborious that such observations are rarely employed in actual casework, and nothing more than noting whether hair is dyed or not is generally done. Then, for effective application of hair cross sectioning to morphological examination of dyed hairs, the sectioning method for hair samples was improved and cross section morphologies of dyed hairs made with a newly improved method were compared among Japanese females. It requires a lot of time, labor and skill to make cross sections of hairs with the conventional hair cross sectioning method of using a celluloid plate as an embedding material. Cross sections of hairs can be made easily using the Technovit 7100, an embedding resin system based on glycol methacrylate. Cross sections made with the ’Technovit method’ are of equal thickness and perpendicular to the hair shaft so that cross section morphologies such as a thickness and damage of cuticle, density of melanin granules and state of dyeing can be accurately appraised. In cross sections of dyed hairs collected from twenty Japanese females, several peculiar morphologies that give useful information for morphological comparison were observed.

This paper reports a comparison study of headspace sampling with microextraction devices for detecting an accelerant such as motor gasoline from fire debris collected at the fire scene. Microextraction devices compared solid-phase microextraction (SPME) device and improved gastight syringe. This microextraction device is made from 250 μL volume gastight syringe and 6-cm length GC column. The inside of this short GC column is mounted with an activated charcoal powder. Extraction procedure is performed by the strokes of the plunger in this microextraction gastight syringe (MEGS). The extraction of volatile organic compounds with MEGS is the same as the principle of the dynamic headspace concentration with an absorption tube. Compared to SPME, MEGS is a practical device for headspace sampling of volatile organic compounds with high concentration capability.