Date of Submission

5-2026

Document Type

Thesis

Degree Name

Master of Science in Forensic Science

Department

Criminal Justice

Advisor

Josep De Alcaraz-Fossoul, Ph.D.

Committee Member

David San Pietro, Ph.D.

Committee Member

Nikolas Stasulli, Ph.D.

Keywords

Latent Fingerprint Microbiome, Time Since Deposition (TsDp), Environmental DNA (eDNA), Friction Ridge Degradation, 16S rRNA Sequencing, Environmental Factors

MeSH

Microbiota, Dermatoglyphics, Forensic anthropology, Environmental DNA, RNA, Environmental exposure

LCSH

Fingerprints, Human microbiome, Forensic anthropology, Environmental DNA, Nucleotide sequence, Environmental toxicology

Abstract

Latent fingerprints (LFs) are a well-established type of forensic evidence that rely on friction ridge patterns for human identification. Additionally, they host a varied community of microbes (skin­ transferred microbiomes) that are potentially influenced by various external factors, including environmental and human activity. LF microbiomes have several forensic applications, such as aiding in the identification or geolocation of individuals and estimating time since deposition (TsDp). However, the influence of environmental DNA (eDNA), or small genetic traces in the form of sloughed off skin cells, pollen, spores, and even whole organisms, is still poorly characterized. Therefore, the reliability of such LF microbiome-based analyses may be compromised by eDNA inadvertently deposited onto surfaces through human activity or ambient exposure. This study investigates how varying levels of human traffic and environmental exposure may influence the dynamics of native LF microbiomes over time. In this experiment, LFs from six (6) donors were deposited on glass microscope slides and placed in six (6) environmental conditions varying in light exposure (OPEN and CLOSED), human activity (HIGH and LOW), and environmental exposure (INDOOR and OUTDOOR). Samples were analyzed at 24 hours, 3 days, and 30 days post-deposition. 2D and 3D imaging techniques assessed friction ridge degradation over time, while microbial community profiling was conducted with 16S rRNA gene sequencing. Microbial composition was examined at the family taxonomical rank to evaluate temporal changes and the effects of eDNA. 2D and 3D analyses revealed varying levels of friction ridge degradation depending on the influencing factors, with 3D metrics showing greater sensitivity. Microbiome results revealed that while total microbial abundance remained relatively stable, community composition and diversity changed significantly over time, particularly under outdoor conditions. To better interpret these changes, taxa were categorized into groups based on specific criteria, allowing for differentiation between native LP-associated microbes and environment-related DNA. These shifts were largely driven by the increasing influence of eDNA over time. Together, these findings demonstrate that LF microbiomes are dynamic ecosystems impacted by environmental factors, highlighting the importance of accounting for these conditions in LF aging analyses.

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