Generally, in the analysis of the accident between the car and the pedestrian, an index called Wrap Around Distance (WAD) is used to quantify to the positional relationship of the pedestrian's head because the pedestrian falls so as to wrap around the front shape of the car. There are a few reports in Japan that the relationship between the WAD ratio and the impact speed was expressed by linear regression based on the assumption that the position where the pedestrianʼs head collides moves to the rear of the car as the impact speed of the car increases. However, the coefficient of determination in the linear regression is so small that the behavior of the pedestrianʼs head during the collision was not properly described. It is inappropriate for the accidental reconstruction to apply WAD in estimating the impact speed of the car.

 We created the mathematical model that predicted the positional relationship between the pedestrianʼs head and the car analyzing 56 accidents. Our model described in detail the behavior of the pedestrianʼs head by considering both the behavior of the pedestrian during the collision and the deformation of the car. As a result, our model indicated that the behavior of the pedestrianʼs head changed the distance from the height of the front edge of the hood to the pedestrianʼs center of gravity, and the position restricted the upper limit by visualizing the simulation results for 7 data.

 The importance of image analysis in the forensic science field has been increasing rapidly alongside the increased usage of security cameras. Specifically, the analysis of geometric information, such as position, length, and shape (i.e., vehicle speed measurement, height measurement, and gait analysis, respectively), is in high demand. In this paper, we aim to understand the mathematical principles of geometric image analysis and to expand its range of applications by using data-driven analysis. We created a set of image geometric analysis programs for legal engineering appraisals related to the following two topics: 1) lens distortion correction, and 2) analysis of the perspective projection image (s).

 Regarding lens distortion correction, an existing method of analyzing a single-parameter model from a single straight line has been extended to a data-driven framework that analyzes multi-parameter models from multiple lines. As a result, high-precision distortion correction has become possible by expanding the model even when lens radial distortion is strong and the distortion center does not coincide with the image center. Furthermore, even when the region of interest (ROI) is located near the periphery of the image, the information loss due to resizing and/or multiple interpolations can be avoided by performing one interpolation with translation and enlargement.

 Regarding the analysis of the perspective projection image (s), we revisit classical analyses that use direct linear transform (DLT)-based projection matrix estimation and Gauss-Newton (GN)-based external parameter estimation. In the case of DLT, it can be understood that there is a unified approach for both 2D-2D correspondence analysis (planar projective transformation) and 2D-3D correspondence analysis (3D camera calibration). The analysis based on line correspondence, which has not yet been utilized in the Japanese forensic field, is introduced. By experimentally comparing the three methods based on point correspondence, line correspondence, and both point and line correspondences, respectively, it was revealed that the combined approach tended to be more precise. In the case of three-dimensional-position estimation, where it was pointed out that analysis can be possible even when the number of correspondences is small, and that the field-work procedure is not necessary in the case of relative position estimation. It was shown that multi-view-based 3D human surface reconstruction is possible even in the case of low surveillance camera resolution and non-synchronized settings.

 In Japan, forensic examination of cannabis seeds requires proof of “being cannabis” and “being germinable”, and is currently conducted by continuing cultivation of the seeds for several weeks after germination tests and performing morphological observations and chemical analysis on the true leaves. We have previously constructed a rapid and simple method for identification of cannabis seeds by combining the color reaction with DNA testing. In this study, the effectiveness of the cannabis seed identification methods by combining the color reaction, germination test, and DNA testing that does not involve a cultivation process was verified on seized cannabis seeds.

 As previously reported, the combination of the color reaction using 2,3,5-Triphenyl-2H-tetrazolium Chloride and DNA testing using a commercial kit proved that the seized materials were germinable cannabis seeds within one day. Furthermore, the germination test, in which the young roots and cotyledons were visually checked one week after sowing, was able to more directly confirm germination ability. In addition, DNA testing was possible for the young roots after germination, indicating that they were cannabis.

 This study shows that the methods of cannabis seed identification, which does not involve a cultivation process, are effective even for seized materials whose storage conditions are unknown.

 We examined the decomposition behavior of 1-acyl-substituted derivatives of d-lysergic acid diethylamide (LSD), such as 1-cyclopropanecarbonyl LSD (1cP-LSD), 1-acetyl LSD (ALD-52), and 1-propionyl LSD (1P-LSD) through gas chromatography/mass spectrometry (GC/MS). It was reported previously that in methanol, 1cP-LSD completely decomposed into LSD during GC/MS. We found that in methanol, 1cP-LSD remained undecomposed during GC/MS, and the extent of decomposition varied based on the analyses performed in this study. As a result of a detailed examination, we deduced that the decomposition occurs at the inlet, regardless of the inlet temperature or the type of the inlet liner. We observed that the peak areas of 1cP-LSD decreased with the deterioration of the inlet liner, and this was considered to be a cause for the variation between different analyses. While the acetonitrile solution of 1cP-LSD provided relatively robust results, the other examined solvents showed a significant decomposition of 1cP-LSD and/or a sequent decrease in the peak area of 1cP-LSD with time after the replacement of the inlet liner. ALD-52 or 1P-LSD in acetonitrile were stable during GC/MS, however, they were unstable when methanol was used as a solvent, similar to 1cP-LSD. This suggested that a similar decomposition and/or a sequent decrease in the peaks of ALD-52 and 1P-LSD during GC/MS can be expected.

 While kerosene and gasoline are the most common fire starters used in arson and other crimes, gel fuel is also used sporadically. In forensic science, analysis of gel fuel has been limited to the detection of methanol as the major component, and no cases of discrimination have been reported. In this study, we collected 26 gel fuel products from 13 companies and performed instrumental analyses such as headspace gas chromatography/mass spectrometry (HS-GC/MS), gas chromatography/mass spectrometry (GC/MS), and liquid chromatography/mass spectrometry (LC/MS). In addition, scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), Fourier transform infrared spectroscopy (FT-IR), and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) were also performed on the dried solids of each sample. The samples were then classified into eight groups according to the combinations of components detected by HS-GC/MS and GC/MS and dyes detected by LC/MS. Moreover, principal component analysis was conducted using pyrograms of Py-GC/MS, and amines and their pyrolytic products were used as indicators to differentiate the groups. Combining the components detected using Py-GC/MS with the SEM-EDX elemental results, it was possible to classify the same eight groups from the dried solid samples.

 We developed a new marijuana field test kit that can discriminate ⊿⁹-tetrahydrocannabinol (⊿⁹-THC), cannabidiol (CBD), and cannabinol (CBN) using thin-layer chromatography (TLC). The kit pre-colors the samples at the time of extraction prior to development by TLC, thereby improving the ease and speed of operation at the investigative site. Using this kit, ⊿⁹-THC in the sample could be detected in approximately 10 minutes.

 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.