Should innocent people be on the DNA database?

by Carl Gardner on April 28, 2010

It’s unfashionable to say yes, but I was defending that position again in the Times last week.

Some say that DNA taken from some suspects on arrest can legitimately be compared with unidentified DNA from unsolved crimes. So it’s all right for police to use the DNA of innocent people to investigate whether they’ve committed unrelated offences in the past; but not to use the same profiles later to see if they’re linked to a future crime. How can you agree to the first, if you claim the second breaches the presumption of innocence? The distinction is one of timing, not principle.

Actually the Times edited this part of my piece for some reason: what I originally wrote was that Liberty themselves accept DNA taken from suspects on arrest can legitimately be compared with unidentified DNA from unsolved crimes. Anita Coles’s reply to my piece confirms that. So Liberty’s approach to DNA is not as consistent or principled as first appears.

I also said:

The DNA database is in its infancy: to strangle it at birth would be a disproportionate response to unreal fears. We don’t yet know how vital it may be to keep the DNA of innocent people, and how many serious offenders it will enable us to catch and stop. Only experience and and research will show us.

If we took Liberty’s approach, how would we ever know?

{ 8 comments… read them below or add one }

1 James Medhurst April 28, 2010 at 11:18


The problem is that keeping the DNA only of people who are arrested is itself incoherent. It would solve more crimes if everybody was required to be placed on the database and the current regime suggests that Middle England is allowed “one free crime”. The justification for this approach is surely that people suspected of crimes are more likely to be criminals than those who are not. I have not seen much evidence for this but, if this is the case, then there must become a point where people who used to loiter in town centres (say) but have stopped doing so must be regarded as having moved into a low risk category, whose DNA no longer has to be stored.
.-= James Medhurst´s last blog ..Buckland – the last word? =-.

2 Carl Gardner April 28, 2010 at 11:57

But James, I don’t think the coherence of the current system is based on principle in the same way Liberty’s opposition is (supposedly) based on the principle of “innocent till proved guilty”. The coherence of the current system consists above all in its practicality – keeping the DNA profiles of all those arrested is easy and builds the database while avoiding the need to get everyone to give a sample. I think this is a really good example of a public policy in which practicality is just as important as principle.

It’s Liberty who claim to base their approach on principle (a principle I think is being used out of place). But isn’t that principle completely busted by their acceptance that arrestees’ DNA can there and then be trawled against the database to see if they’re linked to offences they’ve never yet even been suspected of?

3 James Medhurst April 28, 2010 at 16:13

For me, the issue of principle is one of equality. Like you, I do not have a problem with DNA being used to solve crimes. Indeed, I think that it is a very good idea. Given that I think that no privacy is being breached, you may say that it does not matter whether the system is even-handed or not and so it would be possible to fall back on considerations such as practicality.

However, I do think that the retention of DNA does have to be justified on some equal basis, not because it is a breach of privacy to retain DNA but because it is unacceptable to let guilty people go free. The current system is unfair because it gives an unjustifiable benefit to people who are not on the database who, by an amazing coincidence, happen to be the class in power. Therefore, I agree with Liberty that it is necessary to establish some link between being arrested and criminality in order to justify the system. Any such link, if it exists, will necessarily become weaker as time progresses.
.-= James Medhurst´s last blog ..Buckland – the last word? =-.

4 Carl Gardner April 28, 2010 at 17:03

I don’t quite follow your point, James. If the guiding principle were equality, then applying that would result in everyone being on the database, wouldn’t it? If your principle is guilt v innocence, then you create an inequality between those with criminal records and those without; the question is whether that inequality is justified. My approach creates an inequality between those who’ve been arrested and those who haven’t, an inequality I think is justified.

And what’s the “benefit” you mention? I can’t think of any possible benefit of not being on the DNA database – except possibly the benefit of possibly avoiding being caught for an offence I’m actually guilty of.

5 James Medhurst April 28, 2010 at 17:26

I do think everybody should be on the database in which case there is no need to take a principled objection to it. However, I think that the decision to exclude (rather than include) people should be done on a principled basis. Your last paragraph is exactly the benefit that I am referring to – your practicality approach seems to be indifferent to the fact that guilty people are getting off scott-free and makes it look like certain types of crime by certain types of individuals are being targeted rather than crime in general.

Imagine a law which said that if a person reads the Daily Mail, the police will take a less robust approach to considering whether that person is guilty of a crime. This law invades no-one’s human rights and does not result in any innocent people being convicted. But it is still objectionable. Why?

I do not think that it can be justified, in the sense of being proportionate, to rely upon the practicality argument. After all, people who report a burglary will often give fingerprint samples in order to exclude themselves from an enquiry. It would be practical to keep these fingerprints in case the victim later commits a crime but this is not done. The reason why it is not done is because there is presumed to be no connection (causal or moral) between being a victim of crime and committing a criminal offence. If so, then the same should apply in any case where the link to criminal conduct is remote.
.-= James Medhurst´s last blog ..Buckland – the last word? =-.

6 Clovis Sangrail May 13, 2010 at 16:10

Speaking as a professional statiostician, I find several of these comments shockingly ill-informed.
There is substantial evidence that the DNA database produces false positives. This is, in particular, not surprising since I am reliably informed that when a new sample from an arrested person matches an old one (from someone else) it is automatically recorded not as a “false match” but as an id error-so that the two people are automatically conflated thereafter.
When I hear things like that I can only feel that I should make every effort to keep the number of records very low.

7 Clovis Sangrail May 13, 2010 at 16:10

Even if I can’t spell “statistician”!

8 Clovis Sangrail May 13, 2010 at 16:29

You might also like to note that, as the database becomes more “popular”, word of mouth (amomngst the police) certainly suggests that the planting of DNA evidence by criminals is also becoming quite popular. It’s a good way to cast suspicion elsewhere and it’s reallly very easy to do-much easier than planting someone’s fingerprints-all you need is a used tissue.

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