Why it pays to check the work of the other side: the freeing of Amanda Knox

By Anna Sandiford 04/10/2011 7


In one of the world’s most high-profile cases, Amanda Knox was today acquitted of the murder of Meredith Kercher.

I don’t have personal knowledge of the case but if the media reports are to be believed, inappropriate collection techniques and poor laboratory standards were contributory to the DNA results being deemed unreliable.  An extract from the BBC says:

“Prosecutors said she was killed in a brutal sex game which went wrong. Her throat had been slit and she had been sexually assaulted.  They maintain that Miss Knox’s DNA was on the handle of a kitchen knife – found in Mr Sollecito’s [Knox’s boyfriend of the time] flat and believed to be the murder weapon – with Miss Kercher’s DNA on the blade.  They also said Mr Sollecito’s DNA was on the clasp of Miss Kercher’s bra.

But an independent review disputed those findings, raising concerns over poor procedures in evidence collection and forensic testing, and possible contamination.  It placed into doubt the attribution of the DNA traces – collected from the crime scene 46 days after the murder. “

In cases where individuals are known to each other and share living quarters, DNA results must be handled with much more caution than in cases where DNA from an individual turns up at a scene with which they have never previously had any contact and could not have legitimately have had any contact.

In any case where low template DNA may be involved, appropriate precautions should be taken to minimise the risk of accidental contamination.  Historical cases in particular can suffer with lack of anti-contamination procedures but this doesn’t always stop new techniques being applied – checking whether application of such advanced techniques for old cases is something that needs careful consideration by both the prosecution and the defence.  Insufficient or inadequate sampling techniques shouldn’t have been the case in the Meredith Kercher matter because one would hope that the scientists and scene examiners knew how to collect items – perhaps they didn’t.

I’m sure many more details of the basis of the acquittal will become apparent in the coming days and weeks but this is a timely reminder that work completed by one side in a case should be open for review by the other.  As I usually harp on – forensic science should be fully, fairly, accurately and transparently reported – and that includes allowing proper reviews to be completed.

Without such a review, Amanda Knox would still be in prison.

Perhaps the Italian investigators will lift their game so such contamination issues don’t get dragged up again.


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