DNA database pollution

Lord Justice Sedley may be a senior judge, but he is clearly not an expert statistician, (your report 5 September).

DNA profiles recorded on the national DNA database do not uniquely identify an individual. Matching relies instead on a genetic fingerprint comprising ten points. As the number of people on the database increases, there is a corresponding increase in the number of people likely to match any particular profile and hence a reduction in the usefulness of the database for identifying suspects.

Polluting the DNA database with profiles from innocent people will be counter-productive for law enforcement purposes, leading to trial by database and so infringing the right of citizens to be presumed innocent.


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