The goals of this study were to (a) ascertain human identity capabilities of DNA obtained from latent fingerprints that have been first environmentally insulted and then developed by the deposition of a columnar thin film (CTF), and (b) to determine whether the CTF process and material are detrimental to single nucleotide polymorphism (SNP) analysis.
Fingerprints were deposited on five different types of substrates and aged for 1 day, 7 days, or 30 days while being environmentally insulted under one of the four conditions: 16.6 °C and 60 percent relative humidity (RH) (Condition A), 24.5 °C and 60 percent RH (Condition B), 35 °C and 67 percent RH (Condition C) and a cold condition (Condition D). Then CTF technique was then on 59 percent of these fingerprints. DNA samples from 805 fingerprints were extracted, quantified, subjected to manual library preparation using the Precision ID Identity Panel, and underwent high-throughput sequencing. The Ion S5™ platform was employed to sequence 124 SNP amplicons. SNPs were successfully sequenced from 802/805 samples. Total read depth was consistent across environmental conditions, and majority of samples had 100 percent profile completeness and 100 percent concordance. Anecdotally, libraries that were amplified with a higher cycle number had more ‘Major Allele Frequency’ flags compared to samples amplified with 23 cycle numbers, possibly due to stochastic effects. Neither the substrates nor the CTF process and materials inhibit downstream DNA analysis. DNA of low quality and quantity from the chosen samples can be sequenced using the Precision ID Identity Panel on the Ion S5™ platform which performed well, however, a different approach may be needed if spurious alleles are suspected. (publisher abstract modified)