Date of Award

Summer 7-13-2025

Document Type

Thesis

Degree Name

Master of Science (MS)

Department/Program

Forensic Science

Language

English

First Advisor or Mentor

Mechthild Prinz

Second Reader

Patrick McLaughlin

Third Advisor

Lisa Mertz

Abstract

With lower detection limits for forensic DNA analysis, it is important to have a better understanding of background DNA levels unrelated to the crime to facilitate accurate data interpretation. Duct tape is used in crimes, e.g. to bind victims and seal drug packaging, and may be tested for DNA. To determine DNA background levels, twelve volunteers were recruited to donate a used roll of duct tape from their home. The duct tape was divided into three areas: inside, outside, and sides of the roll, and swabbed for DNA. The average concentration of DNA was determined for the inside (0.0723 ng/µL ± 0.141), outside (0.120 ng/µL ± 0.144), and sides (0.453 ng/µL ± 0.691) areas of the duct tape rolls. An ANOVA test revealed no significant difference in DNA concentration between the different tape areas. The sides of the duct tape had the highest concentration of DNA, which correlated to better quality STR profiles, but overall, there was no significant difference in STR profile quality between the different areas of the duct tape. By swabbing distinct areas of the duct tape individually, it was possible to differentiate single-source DNA profiles from mixtures in three tape rolls. More than 60% of the individual samples were mixtures, with 33% single profiles. For all single-source and deducible mixtures, the volunteer submitting the tape roll was the source of, or the major contributor to, the detected DNA. The results can be used to establish the prevalence of human background DNA on used duct tape rolls.

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