Abstract

Biological evidence, such as blood, is one of the most important types of forensic evidence collected from crime scenes. Blood can provide valuable information that can help identify victims, perpetrators, and give insight into what transpired. However, outdoor environments leave biological samples exposed to changing and often harsh weather conditions that can compromise the evidence’s integrity. Ultraviolet (UV) light and variable temperatures are two major factors that can degrade both the physical and chemical properties of blood. This study aimed to determine the effects of UV exposure on the detection and analysis of human blood using presumptive and confirmatory serological assays and DNA analysis.

Thirty-six drops of fresh human blood were deposited on a white cloth, dried for one week, and divided into six separate groups: a control and five UV-exposed samples. UV exposure was done using an Analytik Jena UV-Crosslink instrument, each UV exposure round being 199.9µJ/cm2. A presumptive Kastle-Meyer assay for blood detection and a SERATEC® HemDirect human specific confirmatory assay were performed, followed by DNA extraction and quantitation using the QIAgility instrument.

All samples, ranging from the control to the highest UV exposure, tested positive in both serological assays. Indicating that UV did not significantly alter blood detection. In contrast, DNA analysis results showed a clear negative exponential trend, with DNA yield decreasing as UV exposure increased. The control sample produced the highest DNA concentration (0.147769ng/µL), while the most exposed samples yielded significantly lower amounts, lowest being for the sample exposed to 10 rounds of UV light (0.00259ng/µL).

The results of this scientific study implicate that pertaining to forensic investigations, while bloodstains exposed to sunlight can still be detected by presumptive and confirmatory assays, their DNA may be too degraded to be fully reliable for DNA profiling.

Semester/Year of Award

Fall 2025

Mentor

Jamie Fredericks, PhD

Mentor Department Affiliation

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Mentor Professional Affiliation

Forensic Science

Access Options

Open Access Thesis

Document Type

Bachelor Thesis

Degree Name

Honors Scholars

Degree Level

Bachelors

Department

Chemistry

IRB Approval Number (if applicable)

6734

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