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Comment by DanBC | Hacker News Reader

> his DNA sample was on record after he had willingly given it to them as part of an investigation into a burglary at his mother's home some years earlier.

This is a worrying snippet. Many people in the UK think that DNA databases should include every citizen. There are often local campaigns of "have your DNA taken, get ruled off our suspect list" when there are murders or multiple rapes.

The police have pushed to include as many DNA profiles as possible.

They don't realise that false positives happen.

Keeping a DNA database of just the criminals means that you don't have to store information from 60 million people (approx current UK population), nor process unneeded data to find matches, nor worry so much about false positives.

The good human rights stuff drops out as a result of good data practices.

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> [The police] don't realise that false positives happen.

Rather, they don't care. Neither do the prosecutors. They don't want to imprison innocents, but they also have a strong incentive to look the other way. That's why, for example, prosecutors fight hard to block initial DNA tests on those already imprisoned. (In the US anyway.)

Indeed. I've recently had an issue along those lines albeit on a lesser scale as a witness. The police were more interested in securing a good case for the CPS than actually fairly evaluating the situation. I was actually advised that my statement should only refer to the facts which were likely to aid a conviction rather than be a fair and balanced account of what happened. The moment a conviction was not obviously going to happen, they recommended that I withdraw my statement before they submit the case to the CPS.

I wrote an addendum sheet for the statement instead stating that they'd asked me to do that. That didn't go down well so I better move to another area if I want any policing or assistance in the future...

For ref, no-one was hurt other than insurance companies in this case. Two idiots bounced a car off each other at 20mph - neither need prosecuting.

Just to clarify. This isn't a false positive in the sense that the DNA test is flawed. The guy's DNA was transferred to the crime scene because he has a skin disorder which causes excessive flaking. But it can happen to anyone.

Every test has a false positive rate and if you scrutinize close enough you can often guess reasons/justifications for those false positives. These rationalizations really aren't so important though--- the crucial bit is understanding that there will always be false positives and making a reasonable estimate for how often they'll occur.

The odds of coming up positive on a DNA test are a lot higher than I would have originally believed:

"DNA matching for criminal cases looks at only a few specific loci and the alleles associated with them, so the chances of two separate people matching come in somewhere around 1 in 7,000" http://www.fluther.com/145318/is-there-a-possibility-that-th...

>There are often local campaigns of "have your DNA taken, get ruled off our suspect list" when there are murders or multiple rapes.

Really? That's just daft. Why would anyone who isn't actually a suspect be susceptible to that line of reasoning?

"Are you hiding your DNA because you know it matches a crime scene, perhaps? Let's have you down to the station for some more detailed interrogation."

That's why.

They have a term for that kind of government - "police state".

I speculate, but "mass hysteria" seems to fit. "These are gruesome crimes; I have nothing to hide; I want to help the police; this is something I can do".

There are a few crimes in the UK that get a lot of press coverage, and I can imagine people living locally feel influenced by that.

England (and Wales, I guess?) has a huge DNA database, something like 4.5 million samples. These are taken from a few volunteers; and from people arrested for crime. If those people are not charged, or if they are charged and acquitted, the DNA sample is still retained. A recent trial in EU meant that we had to put some limits in - we keep innocent people's DNA for 6 years now.

There is a weird disconnect between many English people and privacy intrusions from the state. Lots of people were fine with the idea of a national ID card, and only turned against it when details of cost came out.

Peer calls for voluntary DNA database: (http://news.bbc.co.uk/democracylive/hi/house_of_lords/newsid...)

Brief mention of volunteers: (http://news.bbc.co.uk/1/hi/uk/7532856.stm)

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