The effect of cleaning agents on the DNA analysis of blood stains deposited on different substrates

摘要

A deliberate attempt to remove biological material (using a variety of cleaning agents) is a problem faced by forensic scientists routinely. The substrates on which the blood is supported can also have an inhibitory role. This study aimed to investigate the potential contribution that these factors have on DNA analysis In addition, time between deposition and collection of trace evidence was also considered. Blood samples were applied to a number of different substrates. After drying, the stains were cleaned with chlorinated bleach, soap or disinfectant until no visible trace remained. DNA was extracted from the cleaned areas and PCR performed using the AmpFLSTR~R SGM Plus ~(TM) PCR Amplification kit (Applied Biosystems) In excess of 250 profiles were examined and characterised Heterozygote imbalance (Hbx), split peak frequency (SPF) and stutter proportion (SP) were used to assess the clarity of the electropherograms and the ability to relate evidence and control suspect samples. In this 15-day study, chlorinated bleach had the most pronounced negative effects with respect to the characteristics considered.