07 May 15
The latest DNA techniques remain a major force in the investigation of crime
Recent media comment infers that the very latest DNA profiling techniques may bring with them problems as well as benefits.
Comment centred on the use of the new DNA-17 technique which was launched in July 2014. It was said that because of the increased sensitivity of the DNA-17 technique far more DNA may be recovered from a crime - for example if a light switch at the scene of a burglary is swabbed for DNA it may well reveal DNA transferred not only from the perpetrator but from the homeowner and any other person who may have recently touched the surface. This mixture of DNA may well prove more difficult to separate out than when there is only a single source of DNA.
However, this type of background DNA has been routinely encountered by Crime Scene Investigators and forensic scientists for many years and is not a new problem.
It was frequently encountered using th low copy number or low template techniques introduced in 1999; a highly sensitive DNA technique, now largely superseded by DNA-17. The more sensitive DNA-17 technology just makes this a more frequent occurrence.
Key Forensics expert staff are skilled at interpreting these challenging results using sophisticated software and generating the most usable and relevant profiles from mixtures. By using the new accredited DNA-17 technology there is increased potential to match crime stains to suspects where there is only a very small amount of DNA present or where it has not previously been possible to generate a DNA profile. This is of great value in the investigation of cold cases, where material recovered and subsequently stored at the time of an incident can now be re-tested to see if it is possible to generate a meaningful DNA profile.
In summary, the new more sensitive DNA technique can derive profiles from less DNA than its predecessor and yields more mixed DNA profiles. However, the benefits that this sensitivity, resistance to inhibition and ability to obtain results from degraded samples are far greater than the increased complexity of interpreting mixed DNA profiles. Therefore, offering investigative teams identification opportunities which were not possible as recently as 5 years ago.