Journal of Punjab Academy of Forensic Medicine & Toxicology

Forensic samples received in Forensic laboratories are generally collected by the police officers in unscientific manner. Blood pool or stains, found on crime scene are collected on the cotton swabs or on gauze cloth pieces and without further drying them, are kept in plastic container which leads to degradation. In most of the cases, pieces of cemented or earthy material having blood stains are sent to the Lab for further examination. Advance technologies in DNA profiling (STR analysis) may help to identify the criminals even in case the quantity of biological material is very low but improper preservation reduce the chance of DNA amplification in such cases due to damp nature and presence of soil. In criminal cases like murder or physical assault, DNA profiling may help in identification of crime scene location and transfer of biological materials from accused to victim or vice versa. In such type of cases, the result can be concluded on the basis of DNA profiles generated from different samples collected from victim, accused and the scene of offence. Due to improper preservation and other environmental factors, forensic samples collected from soil, may undergo degradation or may possess some PCR inhibitors which affect PCR and ultimately, DNA profiling. These inhibitors are obstacles for successful DNA analysis especially from the blood lifted from the earthy surfaces. STR profiles generated from such degraded or contaminated samples, usually contains PCR artefacts such as Allelic-drop, multi-peak or partial profiles etc. In this study we have taken 30 samples each from different surfaces from the period of 6 months to 3 years, these are ‘Cotton wrapped in blood and soil’, ‘lumps of Blood stained soil’, ‘blood from the wall plaster’, ‘blood stained cemented floor pieces’ and ‘blood stained black road concrete’. Samples, collected in the form of swabs or the piece of earthy materials by the police officials or forensic Expert were sent to the laboratory. Allelic drop or complete failure of DNA profile was seen from the samples like ‘Cotton wrapped in blood and soil’ & ‘lumps of Blood stained soil’, due to sample-degradation and inhibitors present in the soil. This study concludes that better DNA quantity has been found from the samples in which soil particles were less and from those samples, complete DNA profile was generated.