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?

Good.

AJ

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?

UPDATE 2:

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.