THE USE OF A MIX-450 MOBILE FORENSIC LIGHT SOURCE TO IDENTIFY CRIME TRACES

One of the tasks of forensic science is to improve the tactics of conducting an inspection of the scene, which is largely associated with the use of modern technical and forensic tools used to detect, fix and seize traces and other material evidence in order to disclose and investigate a crime and establish the identity of the offender. However, as practice shows, the use of traditional technical means — portable sources of ultraviolet radiation to detect traces of biological origin (blood, semen, saliva and other human secretions) is not always effective. This is due to the fact that the intensity of the luminous flux of fluorescent lamps is quite low, which prevents the detection of traces during daylight hours. In addition, long-term illumination of the object, over 5 seconds, causes the destruction of the DNA in the blood and semen, which prevents the possibility of its further examination. At the same time, the arsenal of methods and technical means is constantly expanding. For example, a mobile forensic light source “MIKS-450” has now been developed. However, there is no information about the types of traces detected with its use. To fill this gap, the author of the article carried out a set of experiments, the results of which testify to the effectiveness of its use for detecting traces of human skin and preliminary examination of documents at the scene. The author also comes to the conclusion that the possibility of detecting traces of human skin depends on the physical properties of the trace substance (dirty or clean hands, dry or wet), the structure of the trace-sensing surface (smooth, rough), its color, as well as the time elapsed since the occurrence traces.

Evaluating the persistence of laundered semen stains on fabric using a forensic light source system, prostate-specific antigen Semiquant test and DNA recovery-profiling

Semen stains on the clothes of victims of sexual assault can remain as evidence even after garments have been laundered. In this study, we aimed to investigate the effectiveness of commonly preferred methods to detect semen stains in two different fabric types that were laundered with different washing machine programmes and washing powders, and to obtain a DNA profile from the semen stains. For this purpose, a comprehensive study was performed on semen-stained underwear using three different methods for stain detection, confirmation and identification: a forensic light source (FLS) system, the prostate-specific antigen (PSA) test and DNA recovery profiling. With FLS applications, stronger fluorescence was achieved in wash protocols performed at a low temperature (30°C) on semen-stained cotton underwear. DNA recovery between 13.45 and 55.00 ng/µl was obtained by modifications in the DNA extraction step when the effect of temperature and washing powder on DNA recovery was evaluated, and these were enough for short tandem repeat (STR) typing in all samples. This study shows that when semen-stained underwear is washed after a month, some semen stains can be determined by FLS and PSA, and all stains can be identified by STR analyses.