Impact of one-step luminescent cyanoacrylate treatment on subsequent DNA analysis

Quantifying DNA loss in laboratory-created latent prints due to fingerprint processing

Fingerprints, which are associated with touch samples, typically contain a limited amount of DNA. The amount of available DNA can be further reduced when the same touch samples undergo fingerprint processing [1]. The fingerprint development process consists of high-powered lighting (inherent luminescence and UV light) and chemical compounds (ninhydrin, black powder, cyanoacrylate, and rhodamine 6 G) which could reduce DNA quality and quantity. Therefore, forensic scientists often must select one type of analysis over the other due to the destructive nature of processing. DNA and latent fingerprinting are both useful sources for identification, although both can produce partial results. A partial DNA profile may only contain a few alleles, limiting the ability to identify a potential suspect to perform comparisons. A partial fingerprint generally means that only a very small part of the fingerprint is present, which makes comparisons difficult. Because partial results are common, combining data from both fingerprinting and DNA analysis would increase the confidence of an identification of a person. Significant research has been performed to determine if a DNA profile can be obtained from latent processed fingerprints; however, there has yet to be research done in a standardized manner. In this study, we used standardized mock "fingerprints" in order to reduce fingerprint DNA variability and specifically focused on DNA quantitation after each step in the fingerprinting process. Results suggest that latent print processing techniques used on non-porous surfaces (plastic, duct-tape, metal, and rubber) do not affect DNA quantity or quality. In contrast, ninhydrin, a chemical used for processing fingerprints present on porous surfaces (wood and paper), significantly reduced DNA recovery. Together these results suggest that DNA can still be performed on latent print processed items, unless ninhydrin has been used.

Interpol review of fingermarks and other body impressions 2016-2019

This review paper covers the forensic-relevant literature in fingerprint and bodily impression sciences from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20 Review%20 Papers%202019. pdf.

A subsequent procedure for further deciphering weapons after application of the Trace Metal Detection Test (TMDT): Proof of concept

The trace metal detection test (TMDT) is an effective and convenient technique to potentially link perpetrators and metallic weapons by comparing morphological information of developed imprints and suspected weapons. However, metallic items without characteristic patterns and incomplete contact with weapons often lead to inadequate morphological features in developed imprints on hands, resulting in difficulty in identifying suspected weapons and a failure to demonstrate potential relationships between perpetrators and weapons. This paper presents a subsequent procedure, after application of the TMDT, for inferring possible weapon-source of a specific imprint. As a proof of concept, all the experiments involved metallic items as an example and were carried out under controlled laboratory conditions. An analytical method was established by selecting elements of interest in developed imprints from seven metallic items (three groups), undertaking quantitative ICP-MS determination of the elements, and comparing the elements in these imprints (inter- and intra-group comparisons) and with those in their source items. Using the established method, possible groups and types of source metallic items could be inferred based on elemental characteristics in imprints, under the premise that no other metal sources exist before or after contacting specified metallic items. This method could be useful for providing investigative clues and evidence of association for developed imprints that lack unique morphological features and for verifying the results of color reactions in the TMDT. For this reason, it can serve as a standard supplementary procedure after the application of the TMDT, which could further strengthen the correlations between perpetrators and weapons even common metallic objects.

Detection of latent fingermarks and cells on paper

Fingermarks and DNA are valuable traces in forensic investigations potentially allowing for the identification of the source of the trace or highlighting a link between a touched object and an individual. These traces are often latent and need to be detected before recovery. While a number of validated methods exist for fingermark detection, no routine method is in place for the detection of DNA. This study investigates the use of pdimethylaminobenzaldehyde (DMAB) in conjunction with indanedione zinc (IND-Zn) for the detection of latent cellular material and fingermarks on paper. The aim of this proof-of-concept study is to determine the successfulness of this reagent (DMAB-IND) in the detection of the respective traces and observe the impact it has on the resulting DNA profile. It was found that latent fingermarks and the associated cells could be visualised following treatment with the reagent. Samples treated with DMAB-IND showed a significantly higher percentage of alleles called compared to IND-Zn-treated and untreated samples due to the targeted recovery of cells. However, the reagent appears to degrade DNA at a rapid rate, requiring the treated samples to be processed for DNA on the day of treatment.