Year of Award

2019

Document Type

Thesis

Degree Type

Master of Arts (MA)

Degree Name

Anthropology (Forensic Anthropology Option)

Department or School/College

Anthropology

Committee Chair

Dr. Meradeth Snow

Commitee Members

Dr. Kirsten Green Mink, Dr. Christopher Palmer, Joseph Pasternak

Keywords

Storage, cross-contamination, evidence

Subject Categories

Biological and Physical Anthropology | Other Anthropology

Abstract

When packaged genetic evidence samples are stored in close proximity, there is a higher chance for cross-contamination, which can lead to potential false results. The goal of this study was to test DNA storage methods and environments to determine the best way to avoid potential cross-contamination. Established protocols for storing different types of genetic evidence samples were evaluated: biological swabs and DNA cards. A known concentration of pig DNA was introduced to the evidence samples. Three different evidence drying times of the DNA-free swabs and cards were implemented before packaging: immediate packaging, an hour drying, and 24 hours drying. The samples were then placed in the evidence envelopes in one of two ways. The first was with a DNA carrying swab/card in an envelope next to a non-DNA carrying swab/card in a separate envelope. The second was with two swabs/cards in the same envelope, one carrying DNA and the other not. The three drying methods and two packaging methods were completed in triplicate. A control sample of a non-DNA carrying sample was also included for both packaging techniques. The samples were placed into room temperature storage and aligned next to each other for different intervals: 72 hours, two weeks, and two months. Once the sample exposed to DNA was removed from storage, DNA analysis was completed to determine if cross-contamination occurred on the blank sample at the same time.

DNA can be a vital piece of evidence in a court of law, therefore the integrity of the DNA is important. If cross-contamination occurs during storage, then the integrity of the evidence becomes jeopardized. Not only does cross-contamination render the genetic evidence problematic; but if left undetected, it has the potential to link an individual to a case they were not actually associated with, or render a genetic profile contaminated and unusable. Either scenario is not ideal and can be detrimental to individual’s lives and the judicial system. If storage methods can cause evidence contamination, then new ways to preserve the integrity of evidence must be analyzed.

Cross-contamination is a rising problem throughout all aspects of a case. Prior studies have found cross-contamination occurring during collection and transportation due to materials or procedures (Fonneløp et al., 2016; Basset and Castella, 2018). Little prior research focused on contamination occurring during storage. This paper will impact the forensic science community by introducing the need for strict regulation and procedures for genetic evidence storage due to the potential of evidence cross-contamination.

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© Copyright 2019 Samantha L. Ramey