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The Role of The Crown Prosecution Service

The Crown Prosecution Service is the government department responsible for prosecuting criminal cases investigated by the police in England and Wales.

As the principal prosecuting authority in England and Wales, we are responsible for:

  • advising the police on cases for possible prosecution
  • reviewing cases submitted by the police
  • determining any charges in more serious or complex cases
  • preparing cases for court
  • presenting cases at court

Find out more about the role of the Crown Prosecution Service

Review of the use of Low Copy Number DNA analysis in current cases: CPS statement


The judgment in the Omagh bombing case, R v Hoey, was handed down on the 20th December 2007.

The Judge expressed concerns about Low Copy Number (LCN) DNA analysis, conducted by the Forensic Science Service Ltd (FSS), which was adduced in evidence. In particular he expressed concerns about the extent to which the scientific validity of the technique had been demonstrated.

LCN is a form of generic Low Template DNA analysis, used when the available crime scene DNA sample is very small, (for example, such as might be obtained from a person's contact with a surface rather than a bloodstain). LCN is the service offered by the FSS, and other low template DNA profiling services are offered by other forensic science providers in the UK.

Following the judgment in the Omagh case on 21 December, as a precautionary measure, the Association of Chief Police Officers (ACPO) wrote to Chief Constables on 21 December 2007 recommending that the police should operate an interim suspension on the use of LCN DNA analysis in criminal investigations in England and Wales. This decision by ACPO was taken following discussion with the Crown Prosecution Service (CPS). The purpose of the suspension was to provide an opportunity to review the situation in the light of ongoing trials in which LCN evidence was at issue, and to ensure that the implications of the Omagh judgment in relation to LCN profiling were addressed before the technique was used in any future proceedings.

The CPS carried out a precautionary internal review of current cases involving the FSS use of LCN DNA analysis. This took place between 21 December 2007 and 14 January 2008.

From this, the CPS has not seen anything to suggest that any current problems exist with LCN. Accordingly we conclude that LCN DNA analysis provided by the FSS should remain available as potentially admissible evidence. Of course, the strength and weight such evidence is given in any individual case remains a matter to be considered, presented, and tested in the light of all the other evidence.

Forensic science has a vital role to play in detecting criminals and bringing them to justice, and equally ensuring that innocent people are eliminated from suspicion. In recent years, the science in this area has developed at a very fast pace, particularly with the growth in forensic science providers who compete with one another to offer an increasingly wide range of new techniques in DNA profiling.

Such developments should ensure such techniques become an ever more compelling tool in the criminal justice system, as long as they are supported by transparent quality assurance processes, set against clear standards, and verified by independent peer review.

This process will be supported by the recent moves to appoint a Forensic Science Regulator; an Interim Regulator was appointed in June 2007, and the permanent Regulator, Andrew Rennison, will take up his post on 11 February 2008. The post of Regulator is also supported by the recent formation of the Forensic Science Advisory Council, whose membership includes representatives from the judiciary and a range of senior criminal justice partners.. In the course of the CPS review, the Regulator provided valuable assistance.

The CPS will continue to work closely with the Forensic Science Regulator in preparing guidance to its prosecutors about the issues that should be considered when Low Template DNA analysis from any provider is potential prosecution evidence.

  1. The regulator has set out his position. This is available as an Annex to this Press Release.
  2. Media enquiries to CPS Press Office on 020 7796 8106.



The Forensic Science Regulator has commissioned an expert review of "low template DNA analysis", including the LCN service offered by the FSS Ltd. The review, led by Professor Brian Caddy of Strathclyde University, began on 8 November 2007[1] and is due to report at the end of February 2008. It is examining the processes used by the various providers; their scientific validity and the way the results are interpreted and presented. Professor Caddy has also been asked to advise upon the creation of a national minimum technical standard for the process.

At present, there is no reason to believe that there is any inherent unreliability in the LCN DNA analysis process provided that it is carried out according to the prescribed processes, and that the results are properly interpreted. In its work so far, the review has found nothing that would indicate any serious flaw in the scientific principles.

The process has been validated by FSS Ltd. in accordance with their internal validation procedures. There is currently no internationally or nationally recognised technical standard governing the validation of low template DNA analysis. Professor Caddy's work will enable the Regulator to prescribe standards against which all suppliers will be required to validate their services.

The Regulator will ensure that the standards exist and that suppliers comply with them in carrying out validation procedures on their forensic science products and services. The Regulator will not, himself, be responsible for conducting external validation of such services."

14 January 2008