Genetics: Databases

Home Department written question – answered on 3rd December 2007.

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Photo of Ian Gibson Ian Gibson Labour, Norwich North

To ask the Secretary of State for the Home Department what estimate she has made of the number of replicated profiles on the National DNA Database; and how many of these are (a) multiple profiles of the same individual under (i) different and (ii) the same names, (b) identical twins or triplets and (c) adventitious matches between different individuals.

Photo of Meg Hillier Meg Hillier Parliamentary Under-Secretary (Home Office) (Identity)

It is estimated that at 31 October 2007 there were approximately 646,890 replicate profiles from individuals on the National DNA Database. If a crime scene profile matches replicate profiles from individuals, a match report showing all the apparent individuals matched will be sent to the force. Thus the presence of these replicate profiles does not impact on the effectiveness and integrity of the database. Nonetheless, a long term exercise is under way to identify issues associated with the removal of such redundant replicate profiles.

Of the 646,890 replicates, 107,966 are due to upgrading samples from the SGM to the SGM Plus method of analysing DNA. When the NDNAD was set up in 1995, the SM profiling system was used which looked at six areas of DNA plus the area sowing the person's sex. In 1999 SGM was replaced by SGM Plus which looks at 10 areas of DNA plus the sex area. SGM has a one in 50 million chance of being incorrect, and SGM Plus has a better than one in 1,000 million chance of being incorrect, when applied to the general population, though they are less discriminating between individuals who are related, or if matched against partial profiles from crime scenes i.e. where the DNA found at the crime scene is too degraded to look at all the relevant areas of DNA. It was decided when SGM Plus was introduced that it was too costly to reanalyse all the samples taken between 1995 and 1999 to upgrade them from SGM to SGM Plus. However, if a match occurs involving an SGM profile, or a partial crime scene profile, the original samples are routinely reanalysed using SGM Plus to provide the best possible match. This may lead to the existence of both an SGM and an SGM Plus profile for the same person.

The information requested on the number of multiple profiles of the same individuals under different and the same names is not available. However, since July 2004 the NDNAD Custodian's Data Quality and Integrity Team has been carrying out a programme to analyse replicate profiles of the SGM Plus type that are shown on two or more Police National Computer records. This work is in support of police operations and is not an exhaustive review of all replicates. It has revealed 3,752 pairs of false/dual identities on PNC where the owning force has now merged the PNC records, and 3,327 pairs of identical twins and five sets of identical triplets on the NDNAD. A marker is entered on the Police National Computer to alert officers to the existence of these twins or triplets.

To date no adventitious matches between unrelated individuals have been discovered where the SGM Plus profiling system has been used.

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