Application of Touch DNA in Investigation Practice / 法医学杂志

With the continuous development of DNA extraction and testing technology, the DNA left at a crime scene plays a decisive role in the determination of criminal suspects in criminal investigation. But in the meanwhile, the anti-reconnaissance awareness of suspect is growing, which leads to a decrease of evidence left at scene during and after a crime. Therefore, in the process of evidence collection at scene, the finding and extraction of touch biological evidence, and the DNA detection are more and more important. At present, the proportion of touch evidence at the crime scene increases, which plays an increasingly important role in the detection of cases. However, with the characteristics of minute quantities, small size and secrecy, these touch evidence is difficult to be observed. What's more, various forms of pollution at the scene greatly accelerate the degradation rate of trace material, thus, the test and analysis of such material has become the emphasis and difficulty of the forensic evidence identification. This article reviews different kinds, collection and extraction methods of touch DNA, the factors that affect the detection and the problems may meet in the detection for providing an application prospect to the forensic practice.

DNA degradation in nucleolus of skeletal muscle, heart, liver, kidney and brain in mice after death / 法医学杂志

OBJECTIVE@#To study the change of DNA degradation in nucleolus of mice organs and its relationship with the postmortem interval, and to investigate a new accurate method to estimate the postmortem interval.@*METHODS@#Eight parameters of cell nuclei were chosen, including the head DNA level, the tail DNA level, the head radius, the tail length, the tail moment, the Olive moment, the head area and the tail area. The changes of DNA degradation were analyzed in skeletal muscle, myocardium, liver, kidney and brain in mice at different intervals (0-72 h postmortem) by using single-cell gel electrophoresis and fluorescent microscope connected with auto-analysis-image system.@*RESULTS@#The tail DNA level, the tail length, the tail moment, the Olive moment and the tail area showed an increasing tendency. The head DNA level, the head radius and the head area showed a decreasing tendency within 72h postmortem in mice. A quadratic regression equation (P < 0.001) and multiple regression equation of DNA degradation tendency were established (P < 0.000 1).@*CONCLUSION@#The regression equations established can be used as a new method for estimating postmortem interval in forensic practice.