DNA Evidence
SCS Circular 3 of 2007 6 March 2007
Issue
1. This circular draws attention to a change in the procedures undertaken by the Metropolitan Police Service for obtaining and presenting evidence of a matching DNA profile.
Background
2. Current guidance on charging decisions based on evidence of a DNA match between a crime stain and a profile held on the National Database is contained in a CPS Policy Directorate Bulletin dated 16 July 2004 entitled "Guidance on DNA charging", summarised in Serious Casework Sector Circular 6 of 2004.
3. In broad terms the guidance provides that a suspect can be charged on the basis of such a DNA match but the need to identify supporting evidence should always be considered where the DNA evidence is not admitted by the suspect.
4. How probative the supporting evidence must be [and whether it is in reality necessary] will depend crucially on the rarity of the match probability. Self evidently a match probability of one in ten million will require very much less supporting evidence to provide a realistic prospect of conviction than a match probability of one in a million.
The Change
5. Until recently, and in accordance with further CPS Policy Directorate guidance issued in March 2006, the MPS standard operating procedures did not require a PACE DNA sample to be taken from a detained suspect in police detention where he had a PNC record with a "DNA confirmed" marker for a sample numbered 96000000 or above.
6. Accordingly, where such a suspect disputed the DNA match at trial reliance was placed on the database match to prove that the crime stains as made by the person in the dock.
7. As many prosecutors and DCWs will know from discussions I have had with them, the MPS has decided to revert to the practice of taking a PACE DNA sample from every detained suspect arrested following a database hit whether or not they have a confirmed DNA marker on their PNC.
8. Accordingly, in the event a case is to be contested and the DNA match disputed, a forensic comparison will be made, on request, between the crime stain DNA and the PACE DNA sample taken from the detained suspect following arrest, to confirm the database match. An appropriate Criminal Justice Act witness statement covering this analysis will be provided for service on the defence in the normal way.
9. It is important to emphasise that requests to obtain confirmatory evidence of the DNA database match is very resource intensive and must only be made where it is clear that the match is in dispute. Prosecutors should liaise with the relevant Borough forensic Manager where confirmatory evidence is being sought.
Confirmed up to date - 05/02/08