Transfer of biological stains from different surfaces

Abstract

Highly sensitive short tandem repeat-based stain analysis of weak biological stains has been improved during the last years. The risk of transfer of cellular material from handled items contaminated with biological stains such as blood and saliva is of forensic relevance. Although the policemen working with crime scene items are very careful, there exists a potential risk of transfer contamination. To obtain estimates for the risk of stain transfer by handling, we have carried out an experimental study on 288 dried blood and saliva stains in two laboratories. DNA quantification showed only small amounts of DNA that could be transferred, especially from stains on paper and cotton. The saliva and especially the blood stains from plastic surface resulted in higher amounts of transferred DNA, depending on the relation of blood volume to included area: Of 192 direct transfers, 17% gave extracts above 10 pg DNA/μl, and only 3% of 96 secondary transfers resulted in amounts above 10 pg DNA/μl.

Everything clean? Transfer of DNA traces between textiles in the washtub

“…The transfer of blood cells from one item to another has been shown repeatedly (e.g., [19,26,27]) and was also frequently possible in our study. Dried blood stains could not only be transferred directly but also indirectly by transfer of tiny dried blood particles as shown by Wiegand et al [26]. This transfer of tiny blood particles seems also possible under wet conditions.…”

“…Saliva samples are less likely to produce full STR profiles after transfer [19,26], especially using cotton textiles as source. This is in line with our results, since no full STR profiles could be obtained after washing buccal swabs together with clothes.…”

“…Direct and indirect transfer of cellular material containing low amounts of DNA from dried blood or saliva spots has been proven by several studies in the past (e.g., [1,13,19,26]), but none of these investigated a transfer by washing. cDNA may be transferred from one textile item to another by washing, especially in a washing machine, often emerges during a trial at court and has to be answered by the forensic expert.…”

Most Common Medico-Legal Autopsy-Related Human and Nonhuman Biological Samples for DNA Analysis

“…For indication of putative nonvictim biological remains, presumptive tests can be applied, followed by an adequate confirmatory test. The proper application of these tests may often result in optimal sampling, however, in the autopsy room, the risk of secondary transfer during manipulation may be elevated [6][7][8][9]. The heterogeneity of potential biological evidences even under slightly varying conditions and quality assurance of medico-legal autopsies [10][11][12][13][14], in addition to scientific considerations and practical experience, may also demand a kind of predictive common sense for deliberation during the sampling process to find the optimal result in context of necessary and satisfactory requirements.…”

DNA transfer: The role of temperature and drying time

“…There have only been a few studies that have focussed on gaining insights into factors affecting such transfer events [1][2][3][4]. A recent review of current knowledge of DNA transfer and implications for casework by Meakin and Jamieson [5] clearly illustrates the need for a better understanding of DNA transfer.…”