Motorization produced traffic accidents and its conflicts to be brought into the court of law. The field of accident reconstruction was born to cope with these litigations. Essentially, traffic accident is a crime of negligence. Punishment and insurance payment depend upon the assessment of the case. Vehicle speed plays an important role in the ratio of fault and plays an important role as a standard of fault authorization. An analysis method has been developed ever since. Now in Japan, traffic accident is punished with a special law independent from the existing penal code. Speed analysis has become a more important factor under this law. Therefore speed analysis has a long historical path and still plays an important field within forensic science. Fundamental method of speed analysis has been long based on the application of basic physics principles. Recent evolution of electrical devices brought another approach to the speed analysis. Images of CCTV, drive recorders, and vehicle mounted electrical data are offering a good chance to analyze vehicle speed. We would like to review the speed analysis of the traditional methods and overview the trend of recent methods of the new era.

 We propose the analysis method of spur mark distance for discrimination of inkjet printers using a measuring microscope. The conventional method is the measurement of the pitch and the mutual distance of the spur marks which depend on the model of inkjet printers. Therefore, it is difficult to discriminate the same models of inkjet printers by the conventional method. First, we established the analysis method to obtain the spur mark distance indented by one rotation of spur gear and examined the difference of the distances in a printer using correlation coefficients. Next, we applied this method to discriminate 60 inkjet printers of the same model. As a result, the correlation coefficients between the same printers approximated to 1. On the other hand, the correlation coefficients between the different printers were widely distributed in the range from –1 to 1. These results indicate that our proposed method can distinguish printers of the same model and be a useful tool for discrimination of printers in combination with the conventional method.

 Gait recognition is one of recently evolving techniques by which we can recognize individuals by one's gait. There are two major approaches; silhouette-based and model-based. In Japan, a method based on GEI (Gait Energy Image), which is one of the silhouette-based approaches, is used for forensic purposes. Sometimes, it is a problem of silhouettes' variabilities in one person due to different clothing that lessen recognition reliability under the GEI method. Here, we analyzed and evaluated the average error rates under clothing variation conditions using the method called Dynamic-features method, which we previously proposed. The Dynamic-features method was built inspired by previous studies of model-based gait recognition, which uses time-series of feature points and local shape features around the points automatically extracted from silhouette sequences. Before analysis, we roughly categorize whole data in the OU-ISIR gait database -treadmill dataset B-, which contains side-view data, into five clothing categories in order to deal with realistic off-line forensic situation, where we cannot strictly control the clothing conditions. As a result, the average increases of average error rate of GEI-based methods due to different clothing were ranged from approximately 8 to 11%, whereas that of the Dynamic-features method was approximately 3%. It was found that two representative dynamics of a feature point of one same person, where the point is influenced by different clothing conditions, showed different mean values but showed similar trends. Based on this fact, it is suggested that robustness of performances in Dynamic-features method under clothing variation conditions is obtained by effective utilization of dynamic properties of human's gait.

 In order to expose substituted, cheated and faked urine specimens submitted for a drug test, a simple and highly sensitive screening method has been developed for the detection of urea in the specimens. This method uses the coloration of a piece of pH test paper which is wetted and set into the headspace of a sample vial containing “urine”, by absorbing NH₃ gas generated by the urease reaction. The present method named, “Urease-Headspace method” (UHS method), was evaluated by applying it to various diluted or adulterated urine samples. The detection limit of urea in water was 2×10⁻⁴%, which was 100 times higher sensitivity compared with a conventional p-(dimethylamino)cinnamaldehyde (DAC) test. The UHS method was applicable even to deeply colored specimens such as bloody urine because the coloration occurs in the headspace of the sample vial. The UHS method quickly revealed the substituted specimens, e.g. water and green tea. Thus, the present UHS method will be effective for the validity determination of urine specimens, which is increasingly crucial in forensic drug examination.

 In this study, we developed a fast screening method for the detection of herbicides paraquat (PQ) and diquat (DQ) in human whole blood, serum, and urine by matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) after solid-phase dispersive extraction (SPDE).

 Prior to SPDE, whole blood samples and serum samples were deproteinized with acetonitrile. PQ and DQ were extracted from these pretreated samples and urine samples by SPDE with Oasis^® WCX, a mixed-mode, reversed-phase/weak acid cation exchange sorbent. The retained PQ and DQ were eluted with the small amount (8 μL) of matrix solution (saturated solution of α-cyano-hydroxycinnamic acid in 1:1 v/v 0.2 % trifluoroacetic acid in water/acetonitrile).

 The extracted PQ and DQ were instantaneously detected by MALDI-TOF-MS in the positive reflector ion mode. The singly charged radical ions M^+· appearing at m/z 186.11 (PQ) and 184.10 (DQ), and the deprotonated ion [M-H]⁺ appearing at m/z 183.10 (DQ) were mainly observed.

 PQ and DQ were successfully detected from even a small amount (0.1 mL) and low concentration (0.05 μg/mL) of sample assumed mild poisoning. The limit of detection (S/N>3) for PQ and DQ were 0.002 μg/mL and 0.01 μg/mL, respectively.

 Five commercial DNA extraction kits for microbial DNA in soil were evaluated in terms of the extraction efficiencies of artificially-spiked extracellular DNA in soil. Commercially-available purified DNA derived from the sperm of Clupea harengus (Atlantic herring) was homogeneously premixed in blank soil samples and extracted using the kits. The spiked DNA in each of the extracts was quantitated by real-time PCR to evaluate extraction efficiency using a specific primer set for the mitochondrial 16S rRNA gene of Clupea harengus. Only the Extrap Soil DNA Kit could extract the DNA from all types of soils spiked at 10 μg/g soil (vegetable garden soil 0.85%, courtyard soil 0.30% and virgin andosol 0.027%), whereas other kits (Nucleospin Soil, Power Soil DNA Isolation Kit, ISOIL and ISOIL for Beads Beating) could not extract the DNA larger than the quantitation limit (0.020%) from the courtyard soil and the virgin andosol which exhibited high phosphate absorption coefficient. Skim milk concentration and bead-beating time using the Extrap Soil DNA Kit were optimized for 20 mg/g soil and 30 s, respectively. Significant PCR inhibition was not observed under the optimized condition.

 N-tert-Butoxycarbonyl-methamphetamine (t-BOCMA), a tert-butoxycarbonyl (t-BOC) derivative of methamphetamine (MA), which has recently been reported in several countries, was seized for the first time in Japan in 2017. It deprotected easily in an acidic condition to result in an illicit MA, and recently became a newly designated drug of the Pharmaceutical and Medical Device Act. For drug enforcement, the information of its properties was, therefore, strongly demanded. In this study, we synthesized the t-BOCMA standard, acquired various analytical data, and demonstrated its conversion to MA in high yield in the relatively moderate acidic condition (5% HCl methanol solution, 50℃). Also, the stability of t-BOCMA in simulated gastric juice (0.08 M HCl, 37℃) was explored by using GC/MS. As the result, 19% of t-BOCMA remained even after 120 min incubation, and the T_1/2 was calculated to be 50 min. These suggest that the orally ingested t-BOCMA would be absorbed into blood in some degree without conversion to MA.

 Triacylglycerols (TAG) are composed of three esterified fatty acids bound to a glycerol backbone and are the main components of several types of edible or cooking oils. An oil such as salad oil is occasionally used for a crime and is left in the crime scene as physical evidence. In criminal investigation, one of important evidence is to identify the kind of oil.

 Therefore, matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) was used for forensic discrimination of oils. In this study, pencil lead as a matrix was used. And this MALDI-TOF-MS with pencil lead technique can potentially be used to identify unknown oil samples for forensic discrimination.

 We experienced a case of successful identification of an unknown body found at breakwater based on root canal treatment. After matching the dental findings of the body to the treatment history of individual's dental records, 23 teeth showed agreement in findings. Although 8 teeth did not agree in findings, they were consistent in terms of dental treatment history. There was inconsistency in the remaining tooth. This tooth was determined as intact, but the dental records indicated the existence of a resin composite restoration on that tooth. However, that inconsistency never became a critical determinant factor. Comparison of periapical radiographs of the body with the dental records revealed that the right mandibular first premolar teeth showed considerable similarity to the images of a broken endodontic instrument and a alveolar bone resorption caused by the leakage of root canal sealer at the middle of the root. Given the above information, we concluded that the identification as the same individual is reasonable. It was thought that a case where the findings of a dental medical accident helped to confirm the identity was unusual.

 Estimating the point of entry and the timing of ocean-drifting human bodies is an important issue for forensic investigation. This study examined bodies found drifting off Kanagawa Prefecture and the Izu Peninsula that had been subjected to medicolegal autopsy. Of 124 autopsy cases commissioned by the Third Regional Coast Guard Headquarters during 2007–2016, 94 cases (76％) were identified, although the point of entry and the timing had been specified in only 10 cases (8％). The cause of death was suicide in 2 cases. The other cases were accidents, such as those occurring during swimming. Long-distance drifting of more than 50 km was observed in 3 cases. In all 3 cases, the accumulated degree days were more than 120℃. Putrefaction had progressed. In one case, the body had drifted 580 km on the Pacific Ocean in 13 days. The drifting distance was correlated with the postmortem submersion interval among drifted cadavers in the ocean currents (r=0.97). A growing need exists for estimation of the point of entry and the timing of ocean drifting bodies in Japan, which is surrounded by large sea areas. We intend to construct a logical analytical system using these actual cases as basic data.