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Single Source DNA Profile Recovery From Single Cells Isolated From Skin and Fabric From Touch DNA Mixtures in Mock Physical Assaults

NCJ Number
253481
Date Published
May 2018
Length
9 pages
Author(s)
Katherine Farash; Erin K. Hanson; Jack Ballantyne
Agencies
NIJ-Sponsored
Publication Type
Research (Applied/Empirical), Report (Study/Research), Report (Grant Sponsored), Program/Project Description
Grant Number(s)
2010-DN-BX-K139
Annotation
The reported research first used the smart single cell analysis method to recover probative single source profiles from individual and agglomerated cells from various touched objects and clothing items belonging to known donors, and then used the same approach for the detection of single source male donor DNA in simulated physical contact/assault mixture samples (i.e. male 'assailant' grabbing the wrist, neck or clothing from the female 'victim', or being in transient contact with bedding from the 'victim').
Abstract
The ability to obtain DNA profiles from trace biological evidence is routinely demonstrated with so-called 'touch DNA evidence', which is generally perceived to be the result of DNA obtained from shed skin cells transferred from a donor's hands to an object or person during direct physical contact. Current methods for the recovery of trace DNA employ swabs or adhesive tape to sample an area of interest. Although of practical utility, such 'blind-swabbing' approaches will necessarily co-sample cellular material from the different individuals whose cells are present on the item, even though the individuals' cells are principally located in topographically dispersed, but distinct, locations on the item. Thus, the act of swabbing itself artifactually creates some of the DNA mixtures encountered in touch DNA samples. In some instances, involving transient contact between an assailant and victim, the victim's DNA may be found in such significant excess as to preclude the detection and typing of the perpetrator's DNA. In order to circumvent the challenges with standard recovery and analysis methods for touch DNA evidence, the researchers in the current project previously reported the development of a 'smart analysis' single cell recovery and DNA analysis method that results in improved genetic analysis of touch DNA evidence. This smart single cell analysis method was used in the current project to recover probative single source profiles from individual and agglomerated cells from various touched objects and clothing items belonging to known donors. The same approach was then used for the detection of single source male donor DNA in simulated physical contact/assault mixture samples (i.e. male 'assailant' grabbing the wrist, neck or clothing from the female 'victim', or being in transient contact with bedding from the 'victim'). DNA profiles attributable to the male or female known donors were obtained from 31 percent and 35 percent of the single and agglomerated bio-particles (putative cells) tested. The known male donor 'assailant' DNA profile was identified in the cell sampling from every mixture type tested. The results of this work demonstrate the efficacy of an alternative strategy to recover single source perpetrator DNA profiles in physical contact/assault cases that involve trace perpetrator/victim cellular admixtures. (Publisher abstract modified)
Date Created: July 20, 2021