title: How long does it take a static speaking individual to contaminate the immediate environment?
abstract: Developments in forensic genetic profiling mean that only a very little DNA is required to generate an identifying profile. However, as this sensitivity increases so does the risk of contamination with non-offender DNA, potentially leading to the conviction of innocents, or release of the guilty. The work of Rutty et al. showed that a static and talking person deposited DNA in front of them within a 15-minute period. This work expands on that of Rutty et al. by determining the time period required for an individual to deposit sufficient DNA for a positive identification to be made, and the distance that this contamination can be detected from the speaking individual. To simulate a scene of crime, sheets of Benchkote(®) were used to represent an area of interest and an unprotected subject talked over them for a variety of times, in a variety of positions (standing, kneeling, and sitting at a desk). Results show that contamination by talking in both kneeling and sitting positions occurred almost immediately (<30 seconds, but not from just one sentence) up to 69 cm from the subject. When standing, contamination could be observed up to a maximum 115 cm from the subject, and was only present in one of three repeats when talking for only 30 seconds. This article illustrates how rapidly a static person can potentially contaminate an area in front of him or herself within a laboratory or scene environment, just by talking.
authors: Forensic Pathology Unit, University of Leicester, Robert Kilpatrick Building Leicester Royal Infirmary, LE2 7LX, Leicester.
authors: Nicholas J
authors: NJ
authors: Port
authors: Victoria L
authors: VL
authors: Bowyer
authors: Eleanor A M
authors: EA
authors: Graham
authors: Madu S
authors: MS
authors: Batuwangala
authors: Guy N
authors: GN
authors: Rutty