DNA, DNA, DNA, DNA, Batman!

Charmless lefty Kerry McCarthy (@KerryMP) has apparently proposed that all 250,000 men in the Bristol area should be DNA tested, in pursuit of Joanna Yeates’ killer.

I have some thoughts and observations, in no particular order.

  • If a man were to refuse to submit to DNA testing, does McCarthy think he should be arrested, and if so, on what charge?
  • On what basis can McCarthy assume that no woman was involved in this crime, which she must since she only wants men to be DNA tested?
  • Why so certain that the culprit(s) live in the Bristol area?

And now, let’s consider the likely costs and logistics of such a scheme.

  • 250,000 men to be DNA tested.
  • I’m going to take a blind guess at the cost of £600 per test, based on the cost of the lab work, as well as police time, administration etc. (See update below for some reasoning behind my guess at the cost, which turns out to be pretty close, actually.)

(I have to assume significant police time would be involved in collecting and processing samples, due to the requirements of the rules of evidence, in the event of any prosecution based on a DNA match.)

  • So, the cost then. 250,000 x £600. That’s £150 MILLION.

A snip, I think you’ll agree.

But how long would this ambitious endeavour take?

Not an easy question to answer, but consider the bottlenecks:

  • Locations for collecting samples.
  • Space to properly store samples.
  • Police officers available for collection and processing work.
  • Capacity of laboratories to work accurately and consistently on the samples.

This last one is a particularly interesting one, since it’s been shown that different labs can easily return different results based on samples of the same DNA, that there are flaws in the process, and miscarriages of justice as a result, that the human element always introduces some degree of error, and that there are intrinsic statistical reasons why accuracy of testing will diminish across a larger sample group.

From 250,000 men, the police could still end up with a shortlist of thousands.

So how long would it all take? 1 year? 5 years? Well… finger in the air again:

  • 240 working days a year. 1000 samples processed a day. 250 days – just over a year.
  • But…1000 samples a day? Hardly possible, is it? To collect that many, let alone process them, is absurd.
  • So lets say 200 samples a day. That means the process could take over 5 years.

Will the police sit on their hands, waiting for a 5 year process to come up with a shortlist of (say) 2,500 men?

I think not.

So, in conclusion, can we agree that Kerry McCarthy is a fucking idiot?



UPDATE: Twittist @PME200 nudged me into trying to put some substance behind my figure of £600 per DNA test.

Well, I haven’t been able to find a definitive number, but:

UK Media report 1 says £500.

UK Media report 2 says (of the same case) £1000.

US Media report says $1000 -$1500 for basic testing, plus much more for further analysis.

Google shows that non-police DNA tests for paternity/heredity can cost £99. However, this cost provides for no police involvement, no chain of evidence, no compliance. Nor does it cost for the emergency logistics involved in such a massive operation, not for any overtime for police/labs working around the clock.

My correspondent, a lawyer, attests that his experience has shown that such basic and cheap DNA tests are worthless at law.

So, for the sake of the argument, will £600 do you?


Via the Ministry of Justice list of approved DNA testing companies, I reached the site of Anglia DNS services, who undertake forensic DNA testing for purposes of investigative identification. They are on the MoJ site as approved for paternity tests. I assume from the wording of their forensic offering that they are also MoJ or ACPO approved for that as well.

For one test, they charge from £450 (dependent on peace of mind or legal), for a 5-10 day turnaround.

For 24hr turnaround add a further £200.

These costs are just for the lab work. They do not include any police time or logistics.

19 thoughts on “DNA, DNA, DNA, DNA, Batman!

    • I think that was proved years ago, and many times over to boot. Has the New Labour Stooge got a grudge that if she was DNA tested everyone else should be too…

  1. presumably, for dna testing to be useful, they must have a dna sample from the villain. this is how they know it’s a man presumably. but then there is the question of why they kept the landlord in for days and spoiled his new year and tarnished his reputation when they must have known straight away it wasnt him. they would have tested his dna on day 1. were they hoping to find something dodgy on his computer and force a conviction out of made up evidence? that would save even more money than mass dna testing!

    on the other hand, perhaps they dont have any dna at all. and the mass screening initiative is just an opportunistic grab.

    furthermore, if you scan all men in bristol, there will be some that match by chance. the probabilities of dna match arent _that_ remote. whomever matches will have their lives wrecked when the papers print “millions to one against” etc. etc.

    • “presumably, for dna testing to be useful, they must have a dna sample from the villain. “

      Well, more than likely, they have a DNA sample from someone they haven’t been able to eliminate as a known contact yet (i.e. boyfriend, landlord, father). That’s very far from being ‘the villain’, or even ‘a villain’.

  2. It’s a variation on “cui bono”.

    We can’t tell whether she’s an idiot until we know what her motive is for making this suggestion.

    If you think her motive is to get the crime solved as quickly and economically as possible, then yes she indeed an idiot of the first water.

    However, as her actual motive is probably that she wants an unarguable way of extending plod’s DNA database by 250,000 records before it finally gets canned under EU orders, probably she is not an idiot at all.

  3. Avon & Somerset police budget is only £280 million. Like most forces, most of that is staff costs. So an alternative use of the £150million this would cost would be a roughly 50% increase in the number of police officers. Perhaps they might help solve it a bit more quickly?

    So yes, idiot she is. Explains a lot of the last 13 years, it really does.

  4. Pingback: Longrider »

  5. Pingback: Longrider » The Insidious Kerry McCarthy and DNA Swabs

  6. But why stop the DNA tests at Bristol’s boundaries? Why not everyone in the UK, while you’re at it?

    Then you have every male on record who thius can be instantly traced and all wrongs righted. Simples!

    Of course I accept it will take a few hundred years to do it, but New Liebour might get back into power by then so it’s looking even better…

  7. With familial DNA most cold cases already turned up hits, there are few people left who do not have someone on the register. 20 line matches? A long way from the “billion to one it wasn’t him”. LCN? Discredited.

  8. The thing is, if I happened to be the killer, male and living in Bristol (which seems to be the specious reasoning behind this idiotic idea of hers) do you know what I would be doing right now?

    Selling my house and moving out of the area because, obviously, if I don’t live in Bristol when they start the DNA testing, I can’t be the killer can I?

    What a fucking waste of rations this woman is!!

    Typical Labour attitude though… They have a Walnut that needs opening. They have a choice between a nutcracker or a sledgehammer. Which would she pick?

  9. Following on the great idea’s from our political elite. It seems the police have decided to interview and arrest the creepy neighbour. Why it took all this time I don’t know.

    I am no sherlock holmes but DNA testing the neighbours(If they agreed) would have been a quick way to eliminate everyone with a key to the building and therefore preferential access to the girls flat where she was heard screaming for help.

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