An excellent blog post by English privacy law experts Amberhawk - "Long retention of DNA personal data has little to do with detecting ordinary crime" analyses official statistics on young male re-offenders to make some telling points about DNA data retention (as I've mentioned previously, even the President of the British Academy of Forensic Science, who is a judge, has criticised the UK's DNA database policy from a human rights law perspective).
Amberhawk point out that 60% of those who will re-offend do so within 1 year (12 months) after their release; 17% re-offend in year 2 (24 months); and there's "significant and pronounced" tailing off towards the end of months 18-24.
They suggest from extrapolating the figures that 82% of those with a criminal record reoffend within 3 years after their release from prison, which supports 3 years as the optimal retention period for DNA to catch most of those who re-offend. Retaining DNA for another 3 years after that (i.e. 6 years) would catch just another 2.5%.
They go on to say that:
"if you factor in the first statistic that “Research recently ... shows that of the male offenders born in 1953, around half of them had been convicted on only one occasion”, and include arguments such as “if someone has not re-offended in three years, then there is a very good prospect that they are not going to re-offend at all” then it looks as if the benefit of DNA retention is around three years and that further retention does very little with respect to ordinary crime"
- and to get 97% of the benefit, the police would only need a 3 year retention period.
The statistics were for periods after release from jail, but the DNA would have been taken at the time of arrest, so we'd also need to factor in some interval between arrest and imprisonment. But even so, there seems little real justification for keeping DNA of offenders more than 3 years after their release - still less retaining the DNA of people who have never been convicted of any crime.
Their speculation - the real reason the police want to keep as much DNA as possible for as long as possible is that they want to use it to help solve serious random crime. But in that case, the government should say so.
For demolition of another specious argument used in favour of DNA retention, see also the Guardian article today "Holding the police to account".
On the Human Genetics Commission report which that blog post referred to, see the HGC press release 24 Nov 2009 and report Nothing to hide, nothing to fear?. Not surprisingly, the report's main conclusion was that Britain's police DNA database "needs to be regulated on a clear statutory basis and supervised by an independent authority". I bet it won't happen, not within the lifetime of this government anyway.
As the Conservatives take the view that "The whole population must not be treated as potential suspects", perhaps things will change when, as seems almost inevitable, they come into power next year. But I'm cynical about whether a party, once it takes the reins of power, will prove willing to get rid of things that might come in handy to help keep it there.
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