Science & Justice最新文献

Touch DNA is one of the most common types of biological material collected during criminal investigations. Diamond™ Nucleic Acid Dye (DD) has been shown to aid in touch sample visualisation and target sampling. It has also been used as a method of shedder categorisation that is cheaper and quicker than DNA methods. However, the DD method routinely involves manual cell counting, which can result in intra and inter-person variability similar to other manual techniques used in forensic science, for example, fingerprint identification. Additionally, DD based shedder categorisation involves counting cells in a portion of the touch deposit to extrapolate an individual’s shedder status, and the sampling effect of such estimations is currently unknown.

The present study tested different data analysis aspects of the DD method, including counting variability within and between people, shedder classification differences based on different counting methods (entire thumbprint, sub-section of a print with most cells, sub-section of a print deemed most representative of the entire thumbprint, and random sections), the use of ImageJ software to semi-automate counting and the use and extension of the DD method for investigating DNA Transfer, Persistence, Prevalence and Recovery (DNA-TPPR).

The results of this study show that there are meaningful differences observed during counting processes both between and within people. These differences tended to increase as the factor of time, or the duration of counting, rather than the complexity of cell deposits being assessed. Investment in cell counting software that eliminates personal factors, such as boredom fatigue, can remedy most of these issues, however, will require optimisation, such as fibre recognition. Shedder testing was shown to be affected by the choice of sampling and categorisation methods, and suggested that using an entire finger or larger section size can provide increased precision. Finally, inverted worn gloves stained with DD may provide an acceptable alternative for hands in DNA-TPPR investigations, providing an interesting alternative for future research.

Traditional forensic chemical comparisons of polymeric materials are often affected by fingerprinting agents that enhance and visualise finger-marks. This can inhibit detailed analysis used to provide an association or discrimination between two samples. In this study, we have demonstrated that the method for polymer comparisons using isotope ratio mass spectrometry analysis is not affected by fingerprinting matter on the surface in contrast to other forensic instrumental tests. A selection of resealable bags was analysed for carbon and hydrogen isotope ratio values of bags that had been subject to various fingerprinting agents and compared to values of untreated bags. The results showed no significant difference between samples that had been fingerprinted from those that were untreated.

Video integrity is a crucial aspect of forensic science that guarantees the reliability and validity of visual evidence used in court proceedings. In an era where digital alteration tools are readily available, ensuring that video recordings remain unmodified is essential to upholding the integrity of the legal system. Our technique offers a new, simple way to check the integrity of video data. Our approach makes use of the BLAKE2b hash function, the blockchain, and the Edwards Curve Digital Signature Algorithm. Video segments are pre-recorded video clips for which signatures are generated and kept in chronological blocks. To provide an additional degree of protection, the signature from the prior block is kept in the present block. These signatures are validated at the moment of validation. According to experimental data, our method performs faster and more securely than state-of-the-art approaches. With negligible extra storage requirements, our approach can detect every kind of counterfeit on any video file, by anybody, at any time. Our security analysis further demonstrates that our approach is resistant to a wide range of attacks, such as side channel, collision, key substitution, and chosen message assaults.

Previous literature has established that recovering heat damaged body fluids is possible, however with little investigation into the effect of accelerants used in initiating arson fires. This study therefore aimed to determine whether presumptive blood detection was affected by heat damage resulting from accelerant facilitated fires. Another objective was to examine various techniques for removing soot, which is a noted barrier to blood detection. The study focused on blood deposited on household flooring materials, one porous and one nonporous surface: carpet and tile respectively. Samples were burned with butane, petrol, and kerosene then presumptively tested using the Kastle Meyer colourimetric blood detection test. Testing was then repeated following soot removal by either wiping, scraping, or using liquid latex. The “strength” of positive detections was evaluated using a scale based on reaction speed and colour intensity. Results demonstrated that accelerants weakened detection strength, although nearly all samples tested positive overall, and the impact of each accelerant on both surface types was largely similar. It was also discovered that soot removal improved the strength of blood detection results in approximately 69% of carpet and 47% of tile samples, with wiping being the superior method on both surface types. Consequently, introducing this investigative step may be critical to maximizing blood evidence recovery in arson casework. These findings indicate the worth in recovering severely burned items, particularly for evidence as crucial as blood.

In some crime scenes, there may be bare footprints. Analyzing and testing the linear measurements of bare footprints in crime scenes can play an important role in personal analysis and individual identification. However, the linear measurements of bare footprints may be influenced by different motion states, leading to changes in length and width or even significant deviations. Previous studies focused on the linear differences between static and dynamic footprints, and failed to take the speed factor into consideration. This paper studied the stability and change regularities of the linear measurements of bare footprints in four different motion states: standing, normal walking, fast walking and trotting. Dust footprints of the right feet were collected from 80 healthy young adults under these four motion states. Seven linear measurements were obtained for each footprint using the Reel method, totaling 2240 data sets. One-way repeated measures ANOVA was used to assess the measurement variations across the four states. The results showed that there were statistically significant variances in the length measurements (A1-A5) between the standing state and other motion states, whereas no statistically significant variances were observed between the three dynamic states. It was found that the mean values of the five length measurements (A1–A5) increased from static to dynamic state, and then gradually decreased slightly as the walking speed increased. Additionally, no significant differences were found in the two width measurements (MPJ Width and Calc Width) between the four motion states. As a preliminary study, this study can provide a reference for the analysis of bare footprints in different motion states extracted from crime scenes.