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More DNA Profiling Mix-Ups

December 01 2012

Forensic Science Interpreting The Evidence

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DNA Profiling

You will no doubt have seen in the national press at the beginning of October the Forensic Regulator’s report into the contamination of DNA samples at LGC Forensics, which led to Adam Scott being charged with rape in Manchester, a city he had never been to.  Now we have uncovered another equally dangerous error in a case also involving DNA profiling of samples.

In the latest mix-up, swabs were taken at separate incidents on the same day by SOCOs from the same police station in Greater Manchester.  The substances swabbed were photographed first and appeared to be spittle at one scene and blood at the other.  The continuity paperwork records that swabs were taken of the spittle and of the blood and sent to the prosecution laboratory for DNA profiling.  The laboratory examination records noted, however, that contrary to the submissions’ documentation and exhibit labelling the spittle swab appeared to be of blood.  The laboratory conducted chemical testing on the ‘spittle’ to satisfy themselves that indeed it was blood; but apparently did not report this unexpected event further.  DNA from both ’spittle’ and blood swabs were submitted for DNA profiling and analysed in the same run.  The samples both produced the same profile indicating DNA from one person only.  Worryingly the laboratory does not appear to have picked this up as an unusual event either.

Mr X was subsequently arrested and charged in relation to both incidents.  He accepted leaving blood at one incident (although not in the manner alleged), but categorically denies having been to the location where the spittle was found, never mind having left blood there.

So whom are we to believe?  The police photographed and documented taking samples of spittle and blood.  The laboratory documented having examined and profiled two samples from blood.  Examination of DNA profiling data does not suggest laboratory cross-contamination at the profiling stage, which suggests, therefore, an error somewhere in the swab documentation/handling process.

Unlike the LGC-Scott case, the defendant cannot easily claim the alibi of never having been to Manchester as he lives in the region – and so the two failures in the prosecution’s forensic process in this case are much less likely to have come to light if it were not for the defence examination by our scientist.  The un-nerving thing for many other cases in which the significance of the science relies on the stated continuity of the exhibits’ handling process, is that, if the swabs taken from the two incidents had both been of blood in the first place, it may not have been possible to come to the same inescapable conclusion as in this case that there had been a mistake.

In summary, if you are uncertain about DNA evidence in a case, get it and its continuity examined properly.

The Keith Borer Consultants’ scientist in this case was Mike Appleby.

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