All this technique does is establish a "link" between the person who's DNA is detected and the object, or person, it was found on. There's no qualitative information about how close that link is: simply that it exists.

So, for example. If you hand someone a bank-note, it has your DNA on it. The quantity is minute, but it's enough to say that you (as well as hundreds or thousands of others) have touched that piece of paper.

Now, if that note is found on a terrorist - or their blown-up corpse, there's a link established between you and that person.

If you happen to be associated with a "likely" group of people, who for whatever reason are under suspicion of a possible involvement (note the fuzziness of these previous statements), then having your DNA as evidence could be all that's needed to "prove" you were involved. The evidence presented in your trial could be along the lines of:

"We've been monitoring Mr/Ms X as an associate of <terrorist> and have conclusive DNA proof of their connection"

This technology is actually negative progress in terms of criminal investigations. Instead of the old "round up the usual suspects and see who talks", the usual suspects are now anybody that the immensely widened net now trawls in. The chances are good that *someone* of the hundreds of suspects can be nicked for something associated with the case. Great for clear-up figures and headlines, terrible for catching the perpetrators (who are still at liberty, to do it all again)

Like a drunk with a lamp-post, LCN is more use to prop up a shakey case than to provide illumination about who dunnit..

The reason they look at only a few key markers is because these are the areas shown to differ from one person to another. Remember that 96% of the hunman genome is shared with chimpanzees so that's 96% which can be ignored immediately.

That was quickly done wasn't it - so much crime, so little time! But specious, one suspects. Unless you read VERY carefully and conservatively you will miss what is being said. No wonder it was trumpted by BBC radio this morning - CRIME LATEST: SUSPECT TECHNIQUE WALKS FREE.

Here is what you need to understand the babble.

"scientifically robust" - theoretically ok, but totally dodgy in the hands of numpties.

"appropriate for use in police investigations." - but not in determining whether to prosecute or to submit as evidence.

"A separate review of past convictions by the Crown Prosecution Service found no problems" - a fundamental principle of natural justice is that no man is allowed to be judge in his own trial. Hello, CPS...?

"DNA techniques offer the police service an invaluable tool in identifying and eliminating suspects" - illustrating the postmodern approach to policing: the criminal is the one who ends up with the conviction (our bases say so), not necessarily identical with the one who committed the crime. Is it still an offence to impersonate a police officer? Hello, 999...?

"He recommends setting up national standards for training, equipment, and analytical procedures." - Apple pie and motherhood rule. The real meaning is that as used as present, it contradicts all the above claims. Illustrating the postmodern approach to scientific scrutiny - first principle: don't bite the hand that feeds. Hello, is there a natural philosopher in the lab...?

"Juries should be given special guidance by a new independent expert body on how to interpret LCN evidence". Clearly forgetting to add "in other words people like me, who can turn around Home Office jobs at a good speed and with the right answers", and quite oblivious to the current unsatisfactory status of "expert witnesses" in giving evidence - especially in relation to statistics and probability. A professional chancer then. So is there an expert witness in the black box...? Or is it a cat and black.

I submit that no "expert" be allowed anywhere near a witness box unless no-one can be found who can present a case as to the probability of that witness being any less than 100% correct.

"Juries should be given special guidance" - as loaded a construction as the prosecution could wish for. If a prosecution rests on technical evidence, then the significance of that to the prosecution case should be put in open court - from the judge presiding to the public gallery. Otherwise juries may as well be given guidance mafia-style. Whacky Jacky has her way.

"Too much focus has been put on reassuring the public" - illustrating the postmodern approach to public interest scrutiny bodies, unless the quote has been pulled out of context.

"It has been used in several high profile investigations worldwide" - and remains inadmissible in several countries.

----------

@James > "Remember that 96% of the hunman genome is shared with chimpanzees so that's 96% which can be ignored immediately."

Ignoring your typo, there is a murder mystery by Edgar Allen Poe you haven't read - it might change your mind about that 96%.

So it's back to guilty unless proven innocent, then? And since you can't really prove innocence (it's impossible to prove a negative, after all)...

"DNA techniques offer the police service an invaluable tool in identifying and eliminating suspects in crime investigations"

Am I the only one scared by the word "eliminating" in that statement? Especially as you brits are now just about as good as us yanks in eliminating/terminating people who just don't quite look, act, or think the "right" way.

It is based on amplifying incredibly small samples.

However, every person leaves very small samples of their DNA on everything they touch, and it's very difficult to fully clean any object.

Therefore, the ONLY possible use for LCN DNA profiling is in 'Cold cases', where they've got a fairly clean slide from an old case that they can re-examine.

Even then it's unreliable, as you're just as likely to match with the lab assistant as with the criminal!

I'm very surprised that I have seen very little discussion on a very simple way to beat the DNA tests.

If I were to break into a place and wanted to cover my DNA tracks, I would do a little planning first. Over a period of several weeks, I'd go around some random hotels and or hospitals and collect used vacuum cleaner bags.

Then I'd pool their contents and put them in small explosive devices (such as a bug bomb style), creating DNA Bombs.

Once I've performed my criminal act (gloved of course), I'd set off the DNA bombs at the scene of the crime.

It would be interesting to see how the forensics teams cope with thousands of different random DNA samples.

Even if they did track my DNA to me, how easy would it be to prove that I was actually there and not just another piece of DNA shrapnel?

...That is assuming they aren't busy tracking the DNA of known drug dealers who happened to use the same hotels which supplied the vacuum cleaner bags...