Published in the December 2006 edition of Counsel Magazine

Since 1902, when fingerprint evidence was first used to obtain a conviction, fingerprints have been commonly accepted as a powerful tool of investigation. However, recent cases show that the evidence should not be so readily accepted. DNA evidence is now also being produced in many cases, with great emphasis being placed upon what appears to be strong evidence, especially when figures such as ‘one in a billion’ are often seen.

When a surface is touched, an ‘invisible’ mark can be left in sweat, which can be made visible with a suitable developer, such as aluminium powder. DNA can be found in many forms, such as in sweat, blood, saliva or semen. Considering both types of evidence are regularly found at the same scene, little consideration is given as to how one type of evidence could impact on the other, sometimes with disastrous consequences.

Contamination of DNA samples is often investigated by examining the handling, continuity and integrity of exhibits when examined at a forensic laboratory, where strict anti-contamination procedures are usually followed. However, research has shown that contamination still occurs. In one report, a bloodstained exhibit was being examined when the Scientist manoeuvred their examination lamp, resulting in DNA being transferred from the exhibit to the lamp. The DNA was still present on the lamp months after the examination, risking DNA being transferred from the lamp, via a Scientist’s gloved hand, onto another exhibit from a different case.

What also needs to be considered are the conditions under which the evidence was obtained from the crime scene, as the circumstances can be far from ideal.

Picture a SOCO arriving at a burglary scene one morning, silver case of equipment in hand. He rings the doorbell and is greeted by the Complainant, ‘Mr. P’, who shows him around his burgled home. The SOCO commences his examination report, assesses what evidence to look for, opens his case and removes necessary equipment, his usual practice being to wear gloves. Firstly, he finds and retrieves a shoe mark, recording details in his report. Next, he takes swabs from blood on a window for DNA testing. Having sealed these in an exhibit bag, he removes his fingerprint brush and aluminium powder from his case and brushes over several surfaces, finding finger marks on the window. These marks are lifted with adhesive tape, placed onto an acetate sheet, and notated. Relevant notes are made, equipment returned to the case, gloves removed and, having been there for over an hour, the SOCO moves on to his next address.

He has a further four addresses to attend, but the next three do not take so long to examine, and he arrives at the last scene less that two hours after leaving the first. At this address, another burgled flat, no finger marks are found with powder, but what appears to be a lip impression is located on the back door. The impression is swabbed for potential DNA evidence and the swabs sealed in an evidence bag. Following the completion of his examinations, the SOCO returns to his office, submits the swabs to the DNA laboratory and the finger marks to the fingerprint bureau.

Some time later, the Police are notified of a DNA identification relating to the last scene. DNA was obtained from the lip impression, and was identified as coming from … … ‘Mr. P’. Nothing further is thought until nine months later, when a serious problem arises at Court.

I was instructed to examine evidence in this case and was called to Court by Defence Counsel, Jacqui Vallejo of Tooks Chambers, who, upon being newly instructed, was concerned the SOCO had been to the Defendant’s own flat, with the Defendant’s DNA later being found at the scene of another burglary. Could the evidence be correct or was the concern entirely justified?

On examining the evidence and from conferences with Experts and Defence Counsel, not only could the SOCO not recall whether he wore gloves, but the same fingerprint brush and powder pot may have been used at both the Defendant’s flat and the last scene. After Defence Counsel requested the examination notes for the three scenes examined in between, it transpired that no fingerprint examination was conducted at two of those scenes, and at the third scene, although a fingerprint examination was conducted, a different brush may have been used. Therefore, the fingerprint brush used at the Defendant’s flat may not have been used again until the last scene.

Research has revealed the potential for DNA transfer via a SOCO’s fingerprint brush and powder, with contamination being more likely if a wet source of DNA, for example saliva or blood, has been powdered over. Following tests on brushes that were in use by SOCOs, DNA components were found on just about every brush tested, in one particular case, DNA was found from at least four people!

The Crown proceeded to offer no evidence and the Judge ruled the Defendant not guilty, stating that it would appear to be "best practice to use a clean brush at each scene, and the Police should adopt best practice. The problem should be gotten rid of".

It is unlikely, for financial reasons, that SOCOs will use a sterile fingerprint brush and powder for each scene, common practice being for the same brush to be used for months. In addition, although some SOCOs may wear clean gloves, they handle the same equipment, such as their examination case, at just about every scene attended, leaving the potential for forensic evidence to be unknowingly transferred from scene to scene, day after day, month after month.

What does this mean to the Defence Barrister? Never accept the conclusions of any scientific evidence, even though you may be under pressure from the Judiciary to do so. The Expert’s opinion is just that, an opinion open to challenge. The Crown’s DNA report served in the ‘Mr. P’ case categorically stated the commonly seen "extremely strong support" and "one in a billion" statistic. It was only in conference that the Crown’s Expert accepted contamination was a realistic possibility, despite the Crown being fully aware through the DCS and mention hearings that the Defence were pursuing the contamination issue.

Consider the SOCO’s notes, rather than just their statement, as these may contain additional information. It would obviously be helpful if these were disclosed with the SOCO’s statement, but if not made available, request them. It was from these notes in the ‘Mr. P.’ case that we established the Crown’s SOCO had potentially not worn gloves.

SOCOs are fallible. They too are over worked and under resourced, so steps can be missed and corners cut. "Best practice" is a phrase often heard, but is usually quickly followed with excuses of why these practices were not adhered to. As failure to follow these practices can have a devastating impact on the evidence, surely an effortless action such as wearing gloves should be confirmed with a simple note in the SOCO’s report. If not, the SOCO’s actions are clearly open to challenge.

Have a checklist of every anti-contamination procedure you can think of, for example, were new gloves worn, at how many scenes had the fingerprint brush previously been used, were all exhibits sealed and documented at the scene, and what happened to the exhibits once taken by the SOCO.

Instruct your own Expert to critically examine the evidence and interpret the findings (bear in mind the CJA provisions of potentially having to disclose your Expert’s details, with the risk they will be contacted). As much knowledge as Barristers have about the law, an independent Expert knows the score and the ‘ins and outs’ of every procedure. Get an Expert you can talk to, we are not (all) aliens! If not for the conferences in the ‘Mr. P.’ case, the contamination argument would not have been. It is not about fishing expeditions or wasting time and money, but neither is it about accepting one Expert’s evidence for an easy life. What if ‘Mr. P.’ had pleaded to domestic burglary because of the supposedly irrefutable forensic evidence?

SOCOs may find forensic evidence at crime scenes, but the question is, where did that evidence really come from?