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.

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

Fingermarks can be exploited for both their ridge detail and touch DNA. One-step luminescent cyanoacrylate (CA) fuming techniques used for fingermark enhancement, such as PolyCyano UV (Foster+Freeman Ltd) and Lumicyano™ (Crime Science Technology), claim to be compatible with DNA analysis as they reduce the need for post-staining to increase contrast of the developed fingermark. The aim of this study was to determine the impact that these one-step luminescent cyanoacrylates have on DNA analysis and how they compare to conventional CA techniques. Four donors each deposited five sets of natural fingermarks, to which a known amount of washed saliva cells was dispensed onto half of each set of fingermarks. Each set was treated with either a conventional CA technique or a one-step luminescent CA technique prior to collection and processing of DNA, with one set left as a non-fumed control. It was found that DNA was still recoverable and detectable following each of the treatments. Lumicyano™ had a similar impact on DNA profiles as conventional CA fuming and with post-stain, however, the degradation effect of PolyCyano UV on DNA was greater than the conventional treatments. For quantities of DNA such as that from touch DNA, the use of PolyCyano UV to enhance fingermarks may impact subsequent DNA analysis by causing allele drop out at larger fragment sizes.

Evaluation of one-step luminescent cyanoacrylate fuming.

One-step luminescent cyanoacrylates have recently been introduced as an alternative to the conventional cyanoacrylate fuming methods. These new techniques do not require the application of a luminescent post-treatment in order to enhance cyanoacrylate-developed fingermarks. In this study, three one-step polymer cyanoacrylates: CN Yellow Crystals (Aneval Inc.), PolyCyano UV (Foster+Freeman Ltd.) and PECA Multiband (BVDA), and one monomer cyanoacrylate: Lumikit™ (Crime Scene Technology), were evaluated against a conventional two-step cyanoacrylate fuming method (Cyanobloom (Foster+Freeman Ltd.) with rhodamine 6G stain). The manufacturers' recommended conditions or conditions compatible with the MVC™ 1000/D (Foster+Freeman Ltd.) were assessed with fingermarks aged for up to 8 weeks on non-porous and semi-porous substrates. Under white light, Cyanobloom generally gave better development than the one-step treatments across the substrates. Similarly when viewed under the respective luminescent conditions, Cyanobloom with rhodamine 6G stain resulted in improved contrast against the one-step treatments except on polystyrene, where PolyCyano UV and PECA Multiband gave better visualisation. Rhodamine 6G post-treatment of one-step samples did not significantly enhance the contrast of any of the one-step treatments against Cyanobloom/rhodamine 6G-treated samples.