Effect of DNA tape lifting on the ability of the ESDA® to recover latent indentations in paper

Questioned documents are often received into forensic laboratories requiring examinations for both trace DNA and latent indentations using an electrostatic detection device (EDD) such as the Electrostatic Detection Apparatus (ESDA®). Such documents can include extortion notes, threatening letters, drug ledgers and paper items related to white powder incidents, to name a few. Debate often arises as to which of the various examinations should be undertaken first. Assessments regarding examination sequencing need to be made on a case-by-case basis with the knowledge that each examination has the potential to compromise others. This article focuses specifically on the effect that the tape lifting process has on the ability of the ESDA to recover latent indentations in paper. The research showed that the tape lifting process had a detrimental effect on the ability of the ESDA to recover and develop latent indentations. At worst, the tape lift can cause tears and areas of the paper’s surface to be lifted whilst at the same time effectively ‘masking’ the indentations, making them difficult for the ESDA to detect. At best, there is fibre disturbance that results in the development of background noise on the ESDA lift; this reduces visibility, definition and legibility of the developed indentations. Given these results, in cases where it is decided that both examinations are required, the ESDA examination should be conducted prior to tape lifting for trace DNA.