Assessment of individual shedder status and implication for secondary DNA transfer

Assessing the presence of female DNA on post-coital penile swabs: Relevance to the investigation of sexual assault

“…In a study on shedder ability, we found that individuals can be divided into high, medium or low ability to shed cells onto inert surfaces. 3 Differences in the propensity of individuals to deposit DNA has also been reported by others. 4 Thus, variations in persons shedder abilities may be reflected in the recovery rate of female cells on the post-coital penile swabs.…”

Secondary and subsequent DNA transfer during criminal investigation

“…While the observations of secondary transfer made by Farmen et al [8] were from low template analysis using enhanced 34 amplifications cycles, the observations made here were all from routine analysis using the manufacturers recommendations (30 amplification cycles). Lowe et al [7] also observed secondary transfer to some extent during standard analysis, but in much lower numbers than the present study, with secondary transfer of high class profiles in more than 50% of the cases and transfer of 10 donor alleles or more in 90% of the cases.…”

“…The initial deposit of DNA must be of sufficient quantity and quality to be detected and a good shedder is more likely to deposit significant amounts. Both Lowe et al [7] and Farmen et al [8] observed the event of secondary transfer of "touch" DNA via an individual to a second object when the first individual involved was classified as a good shedder. The surface of the substrate is a factor that was observed to have an effect on DNA depositions during contact, comparing items held for 60 s, Daly et al [9] found that more DNA was recovered from wood than from fabric, and the least was recovered from glass.…”

Following the transfer of DNA: How does the presence of background DNA affect the transfer and detection of a target source of DNA?

“…Some studies have described the occurrence of secondary DNA transfer [3][4][5][6], while others have investigated key variables affecting such transfer [7][8][9][10][11][12][13][14][15][16][17][18]. However, only a limited number of studies have considered multiple transfer steps, and the correlation between secondary transfer and tertiary, quaternary or further transfer scenarios [10,17,19,20].…”