Age estimation based on the methylation rates of DNA in blood samples can provide useful information for narrowing down candidates of unidentified donors and might be helpful in supporting criminal investigations. In our previous study, we showed that Bekaert's age-prediction model using pyrosequencing can estimate the age of Japanese blood samples with high accuracy. Recently, Garali et al. reported a new age-prediction model that requires a smaller amount of DNA compared to Bekaert's model, using the same platform. In the present study, we validated whether Garali's age-prediction model can be applied to Japanese blood samples. In addition, we verified whether these prediction models can be applied to aged bloodstain samples, which are common in criminal investigations. The accuracy of Garali's model on Japanese blood samples (n=143) was 3.19 years in terms of absolute mean error (MAE) and 4.24 in terms of root mean square error (RMSE), which were comparable to those of Bekaert's model (MAE 3.24 and RMSE 4.12). Although Garali's model alone could predict age with high accuracy, it was suggested that using both models for age prediction is preferrable when DNA yields are sufficient because Bekaert's model could probabilistically reduce prediction error due to marker multiplicity. At nearly all CpG sites examined, no significant differences were observed in methylation rates between aged bloodstain samples (stored for 1 week to 14 years) and blood controls. Similarly, differences in predicted ages between Japanese blood and aged bloodstain samples were very small in both models. These results suggest that both age-prediction models can be applied to aged bloodstain samples with the same high accuracy as when applied to fresh blood, even when samples have been stored for a long period of time.

　Historically, forensic scientists have used the model proposed by John Searle in 1983 to estimate the car impact speed using the throw distance of a cyclist in an accident reconstruction. However, it has not been verified whether the Searle equation originally developed for application to pedestrian accidents can be accurately applied to bicycle accidents. Furthermore, it was designed to calculate only the lower limit value instead of requiring no variable input of the projection angle that cannot be observed. These issues have long been concerns for the forensic scientists who conduct accident reconstruction for the purpose of proving the facts of a crime.

　Therefore we developed a new model for estimating the car impact speed in bicycle accidents using the throw distance of the bicycle and the cyclist. Our model was designed to enable the setting of the projection angle and to calculate the upper and lower bounds so as to include the true value, based on the original equation of the Searle equation. We further verified the suitability and interpretability of the proposed model using data from previously reported crash experiments. Thus the proposed model was consistent with the experimental data, considering the variability of the crash test data, and properly simulated the post-crash motion of the bicycle.

　This research will contribute to widen the scope of the inference in the scene of accident reconstruction in forensic science by providing two independent equations for estimating the car impact speed using the throw distance of the bicycle and the cyclist.

　For this study, we investigated the minimum number of short tandem repeat (STR) and single nucleotide polymorphism (SNP) loci sufficient for personal identification in the Japanese population. A guidance for the data volume that should be treated as personal information was presented here. The uniqueness of individual genotypes was evaluated according to the Scientific Working Group on DNA Analysis Methods interpretation guideline, using the probability that another individual would have the same genotype by chance. In the Japanese population, the threshold of random match probability sufficient for personal identification was 8.15×10^－11. In STR, it was considered that when 9 or more of the 21 autosomal STR loci of the GlobalFiler system were combined, they should correspond to personal information. For SNP, a total of 112 loci should be required for identification when cumulating the number of loci at the minor allele frequency interval of 0.01. However, based on the median of allele distribution, a total of 47 loci were necessary to reach below the threshold. Furthermore, we simulated the number of the required loci when the size of the population was variable. Since genome data is already widely used in society, we need to recognize that strict management of genome data are essential from the viewpoint of protecting personal information.

 In recent years, arson using alternative ignitable liquids such as lighter fluid have been occurring. Detector tubes utilized as on-site detection methods in Japan are specialized for gasoline and kerosene. We investigated the effectiveness of commercially available flammable gas detectors as an alternative to these methods.

 The lower detection limits of the detector and detector tubes for various ignitable liquids were investigated, and the detector showed better results than the detector tubes for those that did not contain aromatic compounds. It also had a better false positive rate than the detector tube for matrix samples that could be found in fire debris. Furthermore, the characteristics of the detector based on the response distance from the ignitable liquid source and the response of the ignitable liquid to the simulated fire debris are discussed, and the optimal use of the detector was proposed.

 The concealed information test (CIT) is a memory detection technique that examines whether an examinee knows crime-relevant information. In Japanese field applications, an expert judge whether the examinee recognizes crime-relevant information by visually inspecting differences in physiological responses to crime-relevant and crime-irrelevant items. This study proposes an improvement of the statistical method for discriminating differential physiological responses that integrates multiple autonomic measures. The proposed method involves (a) weighting of effect sizes based on the consistency of differential physiological responses and (b) utilizing information on the covariate relationships of physiological indices. This method was applied to CIT data obtained from 167 participants. The proposed method exhibited adequate specificity (95%) and inconclusive rate (20%) for utilization in criminal investigations, though the sensitivity (75%) was moderate. The proposed method is expected to improve the validity of the CIT by increasing sensitivity and specificity through its combination with expert judgement.

 In order to detect buried iron items in a natural sand beach, we conducted a magnetic survey with an Overhauser magnetometer. First, a three-meter-long survey line was laid at Yayorigahama Beach in Okayama Prefecture. A steel can, a stainless steel knife, and a plug-in multi-tap were buried at 10 cm. Magnetic field intensity (MFI) and the magnetic susceptibility (MS) were measured on the beach surface. The MS values indicate a relatively higher value at the site where the steel can was buried 10 cm in burial depths, while such an increase was found at the depths of 20 cm, 30 cm, 40 cm and 50 cm. The peak of MFI could be recognized at the depths of 10 cm to 40 cm. This implies that the MFI test with an Overhauser magnetometer is more effective than the MS measurement. Magnetic anomalies of MFI were recognized on another survey line in Yayorigahama Beach where reinforcing iron bars were found at a depth of 90 cm. Our results indicate that the hidden iron items could be detected using an Overhauser magnetometer in the sand beach.

 Forensic samples left at crime scenes are exposed to various environmental factors, and the extracted DNA from them are sometimes highly degraded. It is difficult to set an amount of degraded human DNA template, and allelic drop-outs may occur after PCR amplification and electrophoresis, making STR analysis difficult. In order to obtain useful STR results, it is necessary to know the degree of human DNA degradation in addition to accurate human DNA quantification. In this study, we examined the relationship between the Degradation Index provided by the Quantifiler Trio DNA quantification Kit and the allele detection rate, using degraded DNA prepared by two methods. The amount of the human DNA artificially degraded by NEB Next dsDNA Fragmentase or UV irradiation were determined based on the small autosomal human target of the DNA quantification kit and STR test was performed using the GlobalFiler and Yfiler Plus PCR Amplification Kit. The ski-slope effect profiles in the electropherograms were observed and some alleles of high molecular weight locus were not detected. The large differences in the Degradation Index values and the allele detection rates were observed between the two degradation methods. When the DI was greater than 2.0 for fragmented DNA and 5.61 for UV-irradiated DNA, not all alleles were able to be detected even with 1 ng of DNA template.

 Body fluid identification from crime scene evidence is crucial to determine the type of crime and to verify the victim’s testimony. We previously developed the multiple body fluid-targeted multiplex RT-PCR assay (MM) for simultaneous discrimination of blood, saliva, semen, vaginal fluid and nasal secretion. That procedure enabled precise and comprehensive identification of forensically relevant body fluids, especially in unknown or mixed biological samples. Alternatively, it is possible to narrow down the body fluid type by creating a case summary and performing a presumptive test for the expected body fluid and followed by a confirmatory test. In the present study, single body fluid-targeted multiplex RT-PCR assays (SM) were developed for the individual identification of blood, saliva, semen, or vaginal fluids. The repeatability of SM results was evaluated by using the pooled cDNA of each targeted body fluid and comparing it with the results of MM. Then, the peak height and detectability of each marker were compared between MM and SM on individual mixed and unmixed body-fluid stains. Like MM, the normalized values of SM were well reproduced in repeated electrophoreses. The positivity of the body-fluid markers was also well reproduced in repeated PCR amplifications. The average peak heights of some markers were significantly higher in SM than in MM. The detectability of SPTB, MUC7, and SERPINB13, which showed lower average peak heights among body fluid markers, was improved in SM. Comparable positive detection of other markers that showed sufficient amplification was found in SM and MM. The identification of targeted body fluid was performed based on the criteria we previously proposed, showing highly specific results. In conclusion, SM and MM can be performed individually or simultaneously based on the sample condition or case summary in order to precisely identify body fluid samples in forensic laboratories.

　In recent years, the technology called SfM (Structure from Motion) has been introduced in police works. The technology makes it possible to construct a 3D model (e.g., point cloud data and polygon mesh data) from images photographed in various angles and measure distance on the 3D model. The authors have been promoting its use for traffic accident analysis and offering the 3D model of the accident site for investigative support. This technology has advantages such as saving work time in the site and can be applied to various size objects compared to a 3D laser scanner. Since the 3D model constructed by SfM is in a pseudo shape, it is necessary to verify for accuracy before adopting it to a real case.

　In this paper, we performed three experiments to verify 3D models constructed by the SfM software “Context Capture”. At first, we verified reconstruction accuracy of the vehicle and the road shape by comparing with 3D models made by the 3D laser scanner. Secondly, we assumed measuring distance in a room site and verified measurement accuracy on the 3D model of the room. Thirdly, to measure long distance in large-scale sites, we verified measurement accuracy on 3D models constructed from images photographed by UAV (Unmanned Aerial Vehicle). As a result, reconstructing accuracy of this software is comparable to the 3D laser scanner and that accuracy of measuring distance is accurate enough to use for appraisal and investigative support.

 This study examined the effect of exercise on a physiological level and differential responding during the concealed information test (CIT). Fifty-three participants were randomly assigned to either the exercise group (n=26) or the non-exercise, control group (n=27). After three sets of CIT, the exercise group performed light physical activity for 30 seconds. The control group rested during this period. Larger skin conductance response (SCR), lower normalized pulse volume (NPV), heart rate (HR), respiratory speed (RS), respiratory amplitude (RA) and respiratory rate (RR) were observed for relevant items compared to irrelevant items in both groups. In terms of physiological levels, exercise increased HR and RR, and the physical state changed to more arousal. On the other hand, effects of exercise on physiological responses were observed in RS and RR. The differential responding of SCR and NPV decreased in the second half, but the differential responding of RS and RR decreased only in the control group. It may be suggested that there is an effect to maintain the differential responding of RS and RR by manipulating the arousal level by exercise.

 Performance of the portable stand-off Raman spectroscopic analyzer Pendar X10 was evaluated. Various chemical warfare agents could be detected correctly and remotely. In addition, substances that could be mistaken for suspicious objects were also analyzed, and most of them were detected correctly. It was also possible to detect chemicals through umber colored bottles and paper envelopes, which are difficult to detect with the traditional Raman spectroscopic analyzers. Stand-off measurement up to 2 m and operability while wearing Level A chemical protective clothing was also verified.