For anyone who’s been following the developments in the Stephen Lawrence retrial, the importance of correctly handling exhibits is quite clear with much of the argument of the defence being based upon the reliability of DNA evidence relating to exhibits collected as part of the original case.
Gary Dobson and David Norris are both accused of having participated in Lawrence’s murder. The prosecution are claiming that fibres, blood and hair found on the clothing that was seized from them at the time links them to the scene and proves that they took part in the attack. Their defence council deny this saying that the evidence found is nothing more than evidence that their clothing had been contaminated at a later point.
How then do we as police officers try and ensure that exhibits are treated in such a way that we can rely on them in court?
When we seize items as part of an investigation – be it CCTV footage, clothing or anything else – we commence an audit trail so that we can account for the item’s movements right up to its eventual appearance in a court room.
This means that first of all we’ll write a statement explaining when and where the item was found, what it is and we’ll also give it a reference number so that it can be told apart from other items seized. We also detail what we did with the item after collecting it, for example that exhibit RJS/01 was then transported to Walsall Police Station when it was booked into detained property.
Along with a statement, we’ll also attach an exhibit label which is to be signed by anyone taking control of the item. Once booked into the property system the exhibit’s movements are then logged by the property computer and it will be locked away, again so that we can ensure its continuity.
Whilst keeping a track of an exhibit is important, so too is properly packaging it and taking care to ensure that an item does not become contaminated.
Locard’s Principle is important here – that every contact leaves a trace and that by touching one item and then another, a trace of the first item will likely to transferred across to the second.
This is why when we are investigating a rape, for example, the same officers who have been speaking to the victim will not then go and arrest the suspect as the defence would then be able to argue that any evidence found on the suspect was there because officers had transferred it to him or her from the victim.
As can be seen from the details emerging as the trial progresses, protecting the continuity of evidence can often be very difficult, especially when proving the case comes down to the presence of microscopic fibres on an item of clothing that has been sitting in a property store for eighteen years.
Still, it is principles such as those mentioned above that make the difference in many trials and hence why officers put the time in to ensure that when a case goes to court, they can be confident that they can rely on their evidence.