Contactless DNA Transfer
As DNA profiling techniques have become more sensitive, it has become increasingly apparently that indirect transfers of DNA routinely occur which might result in an individual’s DNA being detected in a place that they have never been or on a surface with which they have never been in physical contact. Recent research has taken this a step further by looking at the potential for a transfer of DNA when there has been no contact at all, sometimes referred to as ‘contactless DNA transfer’.
What do the studies show us?
A study by Olivia Handt and Duncan Taylor considered the levels of DNA that an individual might transfer to untouched items in a working environment. The findings showed that an individual can deposit DNA in within their immediate surroundings even if surfaces and/or objects were not directly contacted. Moreover, DNA could be detected after only a day. Factors which affected the amount of DNA deposited were similar to those involved in secondary transfer and included distance, length of time the individual was in the vicinity of the object and the shedding propensity of the individual.
Two further studies have looked at the potential for contactless transfer of dried body fluids and DNA from used fabric items. The former investigated DNA transfer from body fluids including dried blood, saliva and touch DNA to two non-porous surfaces. The latter took items of clothing worn by donors, used pillowcases and towels and looked at the transfer of DNA to a non-porous surface using gentle shaking of the items above the recipient surface. These studies both showed that DNA can transfer without contact in amounts sufficient to provide full DNA profiles.
How this information can be used
Whilst these studies are relatively limited, they add important data to that already available to an expert when considering the likelihood of DNA evidence given versions of events proposed by both the prosecution and the defence. It is vital that consideration is given to the context of the case circumstances and the range of potential DNA transfer mechanisms is explored, particularly where low levels of DNA matching the person of interest are detected.
Forensic Context’s experts have extensive expertise in DNA transfer issues – contact us by phone or email and we can provide initial free advice regarding whether secondary transfer or contactless DNA issues should be considered.