Date of Award

Spring 5-2021

Document Type


Degree Name

Master of Science (MS)


Forensic Science



First Advisor or Mentor

Mechthild Prinz

Second Reader

Nicholas Petraco

Third Advisor

Grace Axler-DiPerte


Trace DNA evidence may be discovered at a crime scene after having been deposited by a person of interest via active or passive transfer. Based on previous studies, passive transfer of one’s DNA is influenced by their shedding propensity, or probability of depositing a detectable amount of DNA through touch. Determining the shedding propensity of a person of interest can aid in trace DNA interpretation in forensic casework. This study explored STR profile quality and the presence of a DNA mixture for different skin surface locations, including fingertips before and after handwashing. As expected, unwashed fingers showed a higher prevalence of mixtures than washed fingers. Hand dominance showed no significant effect on right versus left finger STR profile quality. However, right-handed participants exhibited a higher mixture prevalence for samples obtained from their dominant hand. Shedding propensity was determined based on STR profile quality and the number of expected alleles detected from washed finger samples only. Three individuals were high shedders (10.7%), 18 individuals were intermediate shedders (64.3%), and seven individuals were low shedders (25.0%). No trend was seen for shedding propensity, profile quality, or mixture status based on biological sex. STR profile quality can be affected by various factors and future research will combine the use of STR results with quantification data to develop an alternative method of predicting shedding propensity.



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