One of the Liberal Democrat policies is that the UK National DNA Database should only store DNA records for proven criminals. I didn’t feel that comfortable with this policy as currently holding records for everyone the Police come into contact with has helped them fish for perpetrators. I had thought DNA evidence infallible.

That was until reading about a study to compare DNA labs and ‘experts’. It transpires that new techniques using tiny DNA samples is not black or white but very grey and actually subjective in the evidence it gives. Also shown that all DNA evidence has to be thoroughly checked to ensure best practice followed.

I’ve served on a jury and along with everyone else would have assumed DNA evidence was unique and cast iron evidence. How naive of me/us. Well with a sufficiently big sample it can be but with small samples, machine errors, technique it’s not. The techniques can give false positives and the DNA forensic experts have been shown to be influenced in interpreting DNA evidence to fit the expected perpetrator.

A statistical geneticist from UCL is quoted in one article “My point is that number juries are provided with often overstates the evidence. It should be a smaller number”.

In fact one US case, using the same DNA material, different experts put the odds from 1 in 2, 1 in 13, 1 in 17, 1 in 47 to 1 in 95,000!

So I no longer think a UK National DNA database is wise or good public policy. It means innocent people with out sufficient resources must be being highlighted as suspect when they should’nt be. I wonder how many people have been jailed wrongly and the real criminal left free to re-offend.