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DNA Evidence

Answer

It is not necessarily straightforward to say that an arrest is made on the basis of DNA evidence, as police investigations will often involve looking at several different types of evidence including DNA, and an arrest may be made on the basis of the whole package of evidence. We are, however, aware of two cases in which arrests were made on the basis of mistaken DNA evidence since the establishment of the NDNAD in 1995.In October 1997 a bloodstain from the burglary of a dwelling was matched to a Mr. K who was arrested by the Metropolitan Police. In fact samples provided by Mr K. and Mr. H had been accidentally switched in the laboratory. Mr K. began legal action against the Forensic Science Service but did not complete it within the legally prescribed period.In August 1999, Mr E. was arrested on the basis of a DMA sample found in a burglary 150 miles from his home. He was suffering from Parkinson's disease and could not have got to the crime scene unaided. This was an SGM match—use of the more discriminating SGM plus technique (explained as follows) showed the first match was incorrect and the charges were dropped.These errors must be seen in the context of almost 300,000 matches between crime scenes and individuals during the period 1998-99 to 2005-06. Use of DMA profiling is an extremely reliable technique.Continuous quality monitoring of suppliers is carried out through the NDNAD's supplier accreditation section, and barcode and electronic document scanning systems are used in laboratories to minimise the possibility of human error.The SGM technique introduced in 1995 looks at six areas of DMA plus the area showing the person's sex and has a one in 50 million chance of being incorrect (the odds are very probably much better than this).Home Office Circular 58/2004 and the ACPO DMA Good Practice Guide advise that where a match of a crime scene to an individual involves an SGM profile, strong consideration should be given to upgrading the SGM profile to SGM Plus to ensure that there is still a match.If a person is to be charged on the basis of a DNA match, the CPS require that there must be supporting non-DNA evidence available to be used in evidence. No-one is ever prosecuted solely on the basis of a DNA match; the DNA evidence is one piece of the information that the courts would require for a successful prosecution.

Secondary information

Type

Written question

Reference

108546; 455 c133-4W

Session

2006-07

Subjects

Databases Genetics

Link

View this Written question on www.publications.parliament.uk05010922000626