LAUSR

The questions on which judges/prosecutors apply for expertise are mostly about by whom a document was drafted/signed. In this study, a new collective strategy was constructed including a collection method, a modified-silica-based DNA isolation method and a novel purification method on 4 contact traces formed on 4 different paper surface during writing, PCR with AmpFlSTR®GlobalFiler™ STR kit (after experimental comparison between 3 different kits) and identification using CE. This collective analysis approach is more sensitive and superior to its equivalents on questioned documents in literature, because quantifiable amounts of touch DNA and profiles with high loci percentages (100% on day 1, 72.72% after 1 week) were obtained up to 1 week even after the most challenging conditions of sample forming that a forensic scientist can meet; as washing hands just before drafting and using very low pressure in a shorter time (simulating a simple contact real conditions while drafting), using no visualizing technique which damage the document. Using the strategy, 4 most commonly used paper types were compared, to see on which of them DNA could be recovered better. The success of this strategy was shown on the 1 day to 10 years-old real samples from a diary and some archive documents from a law office (including the mix-DNA and different ballpoint pens). Thus, it became possible to show if a person had touched the document, in high sucess rates up to 1 week as a secondary evidence, when primary evidences are insufficient for the detection of document fraud offenses. This article is protected by copyright. All rights reserved.