Date: May 19, 2024
Source: Journal of Forensic Sciences
Authors: Abigail S. Bathrick MFS, Sarah Norsworthy MS, Dane T. Plaza BS, Mallory N. McCormick BA, Donia Slack MS, Robert S. Ramotowski MS
The Impact of Sequential Treatments on DNA Analysis from Latent Fingerprints on Black Polyethylene Plastic
Introduction
In forensic science, both latent fingerprint visualization and DNA analysis are crucial for crime scene investigations. However, the relationship between these processes, especially on nonporous substrates like black polyethylene plastic, remains largely unexplored. A recent study published in the Journal of Forensic Sciences sheds light on this interaction, examining how different fingerprint visualization methods impact subsequent DNA recovery and profiling. This blog post delves into the findings and implications of this study, providing a comprehensive overview for forensic professionals and enthusiasts alike.
Methods
The study involved preparing 91 fingerprints on black polyethylene plastic bags, a common nonporous substrate in forensic evidence. These fingerprints were deposited by a single donor to ensure consistency. The visualization methods used included both single-process techniques (white powder, bichromatic powder, bichromatic magnetic powder) and sequential processes. The sequential methods involved either a laser enhancement followed by RUVIS, CA fuming, RUVIS again, and RAM dye stain, or CA fuming followed by RAM/laser and bichromatic magnetic powder.
DNA was collected from the fingerprints using cotton swabs, extracted with the EZ1® DNA Investigator Kit, and quantified using the Quantifiler® Trio DNA Quantification Kit. The DNA was then amplified with the GlobalFiler® PCR Amplification Kit and analyzed with ABI GeneMapper® ID-X software. This rigorous process ensured accurate measurement of DNA yields, peak heights, and the number of alleles obtained, all crucial metrics for assessing DNA profile quality.
Results
The study revealed interesting differences between the single-process and sequential visualization methods. Untreated samples generally had higher DNA yields and peak heights compared to those treated with fingerprint powders. There were no significant differences in the number of alleles obtained between untreated and treated samples, with only one untreated sample producing a CODIS-eligible profile.
In contrast, the sequential processes showed more variation. Fingerprints treated with a laser enhancement followed by RUVIS, CA fuming, RUVIS again, and RAM had comparable DNA yields to untreated samples but significantly higher peak heights. More alleles were obtained with laser enhancement and up to two sequential treatments. However, the CODIS eligibility decreased with each additional treatment post-laser + RUVIS.
On the other hand, the sequence involving CA fuming followed by RAM/laser and bichromatic magnetic powder resulted in significantly lower DNA yields and peak heights. None of the samples treated with this sequence were CODIS-eligible, highlighting the potential drawbacks of this approach.
Discussion
These findings underscore the importance of choosing the right fingerprint visualization methods to balance fingerprint detection and DNA recovery. The initial laser enhancement was particularly effective, significantly improving DNA profile quality and CODIS eligibility. However, additional treatments tended to reduce these gains, suggesting a more measured approach to sequential processing.
Further research is needed to validate these findings and explore alternative methods for DNA collection and processing from treated fingerprints. By understanding the impacts of different visualization techniques, forensic professionals can make more informed decisions, ultimately enhancing both fingerprint and DNA evidence recovery.
Conclusion
This study highlights the delicate balance required in forensic investigations to optimize both fingerprint visualization and DNA recovery. Methods starting with laser enhancement proved to be particularly effective, offering a promising direction for improving forensic analysis on plastic substrates. However, the inherent variability in DNA amounts within latent fingerprints means that a CODIS-eligible profile is not always guaranteed.
Forensic practitioners must carefully consider the impacts of their chosen visualization methods on downstream DNA processing. By doing so, they can maximize the likelihood of developing useful DNA profiles while still effectively visualizing latent fingerprints.
License and Notes
This article is based on the original study (below). The content is licensed under a Creative Commons Attribution 4.0 International License. Contents may be edited for style and length.
Creative Commons License
Bathrick, A. S., Norsworthy, S., Plaza, D. T., McCormick, M. N., Slack, D., & Ramotowski, R. S. (2024). DNA recovery after sequential processing of latent fingerprints on black polyethylene plastic. Journal of Forensic Sciences. https://doi.org/10.1111/1556-4029.15498
