News & Views

DNA transfer: A question of how and when

Mr Red and Mr Yellow shake hands and transfer their DNA to the other personIn recent years, forensic science has seen a number of significant improvements in the field of forensic DNA analysis.  One of the drivers has been the need to detect ever decreasing amounts of DNA.  The DNA17 technique, in routine use in the UK since July 2014, is much more sensitive than its predecessor SGMPlus, and therefore the spotlight is shining brightly on the issues around DNA transfer and persistence.

What does the presence of an individual’s DNA on an item related to a crime actually mean in the context of the case circumstances?  The presence of a DNA match to a suspect’s profile tells you nothing about how or when the DNA got there.  Scenarios incorporating multiple DNA transfer steps, rather than a single direct transfer, are increasingly being raised in court as potential means for the presence of the defendant’s DNA at the crime scene or on an evidential item.

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A Blueprint for Change

House of Lords Logo white on red backgroundToday, the Lords Science and Technology Committee published their report following their inquiry into Forensic Science.  This was probably the most comprehensive and inclusive inquiry to date taking evidence from all stake-holders in the forensic science arena.  And this time, parties that had previously been tentative in responding to questions were now far more candid and hard-hitting in their responses than in previous inquiries.  Maybe this reflected the urgency of change that is now necessary to prevent the potential collapse of the forensic market and the repercussions that would have for the criminal justice system.  The Lords appear to have realised that we are at a critical point:

“This report follows others that have raised similar concerns, yet the changes that are necessary have not been made, despite acknowledgements that they would be. Forensic science in England and Wales is in trouble. To ensure the delivery of justice, the time for action is now.“

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Chartered Society of Forensic Sciences Long Service Awards

The Chartered Society of Forensic Sciences logoAs the Chartered Society of Forensic Sciences reaches its 60th anniversary this year, Julie Allard and Kerri Allen are both honoured to have received long service awards in recognition of more than 25 years continuous membership. The Society has grown and there have been many changes from when we first joined but we have always found our membership invaluable, allowing us to meet, communicate and collaborate with other members of the forensic community.  Our support of the Society will continue and, as scientists within a small organisation, in particular we appreciate the opportunities on offer for professional development.  We would encourage other forensic scientists to consider joining and enjoy the benefits and opportunities that membership provides.  There is more information on the Society’s website.

Use it or Lose it: Is expertise in some body fluid examinations being lost?

Forensic body fluid analysis includes tests for urine stains As body fluid examinations have become heavily focused on the ability to obtain a DNA profile, the expertise in analysis and interpretation of tests for some of the more rarely encountered body fluids, including urine and faeces, has become limited.  Some of the main forensic providers no longer offer this testing under their UKAS Accreditation.  In a case, reviewed by Forensic Context, in which there was an allegation of the offender urinating onto the clothing of the complainant, the lack of any testing for urine was questioned by the defence and clarity sought as to whether testing was possible or simply not offered by the prosecution provider.

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Can we rely on the DNA match statistic from Specialist Statistical Software?

DNA Mixture software

As DNA profiling methods have become ever more sensitive, the detection of trace amounts of DNA has improved. Hence the number of DNA mixtures we encounter has increased.  This was especially highlighted following the introduction of DNA17 methods in 2014. In many situations the mixtures have multiple contributors and are complex to interpret.  Whilst previously many results were designated as too complex for interpretation, the last couple of years have seen the introduction of ‘probabilistic genotyping software’ packages which enable a statistical evaluation of complex results.

 

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