Fingerprint or DNA evidence – the choice in the 21st century

I was at a launch of a new social development company on Monday morning which had about eight speakers and the guest of honour as well.

One of the speakers was an old colleague of mine from the Police here in Trinidad.

During his speech where he went on to commend the community and main players with this initiative (which is only right) he also stated in no uncertain terms that fingerprints were the only positive identifiers of a suspect. As you can imagine I felt all eyes fall suddenly on me.

Well lets look at it…

Fingerprints – each and every person has fingerprints. No one person has the same fingerprints as the next person. Even twin siblings have different fingerprints. Yep that’s right, twin brothers or sisters have different fingerprints (different from DNA as you will see).

DNA – There is much speculation regarding the usefulness of DNA in the fight against crime. In my view it is a very valuable tool, but that is all it is (as are fingerprint examinations), a tool. It IS possible for two people to have the same DNA but most of the time the chance of someone having that same strain of DNA is set about one in one billion people.  And as there are only six billion people on the planet the chances of them being at that crime scene are remote (although not impossible).

As I have already said, twin siblings share the same DNA. It is a mix of the DNA from both the mother and the father. Brothers and sisters who are not twins are unlikely to share the same DNA because they were conceived at different times and the genetic makeup of the parents does change (as it does in us all).

So why am I dismayed at this particular comment? Well, this man has moved through the police service but was heavily involved in the crime scene department before the courses started being taught at the Specialist Crime Academy. It was called the Fingerprint department before these courses were run because that is all that was concentrated on. But what this man fails to realise is that for every fingerprint you find, you may not get a mark good enough to identify. That mark would then be confined to the bin and never considered for anything further. BUT he now knows, because we taught him and his fellow officers, that DNA can also be recovered from the same mark. So if he has failed to get identification with his comparison of a fingerprint he may still get a match from the DNA found in that fingerprint.

That DNA will be reported on that it has the likelihood of being repeated once in one billion (1 in 1 billion) people. Keep in mind that a person playing the UK lottery has approximately a 1 in 14 million chance of getting the six number jackpot, the chances of your DNA “brother” being at that scene are very remote.

Is that not a better way to look at it? Using a multi-disciplined approach will enable all parties to ensure the right man is caught and prosecuted for his crimes, and ultimately pays the penalty which can be very severe.

Another part of this argument is that fingerprints are fact. They are on your hands and are often left at scenes of crime (not yours I hope).

An expert has to report his / her findings on fingerprints. The comparison and interpretation of fingerprints is NOT fact.

So what happens when you have an individual who has been trained as a so-called expert but is in reality not very good at his job? The only people who will know he is rubbish are his co-workers who often will not say anything because they are either junior to him, scared of him or just plain lazy themselves. BUT when this person stands up in a court of law and declares “This is “His” fingerprint because I am the expert and I say it is!”

Then the fact of a fingerprint is based on opinion.

Opinion of a man who wants to further his career, who wants to ensure he keeps his job, who needs to show the public that the police are putting criminals away… all based on his opinion.

DNA is based on irrefutable scientific fact (as it stands today). Fingerprints are fact but the reporting in court is subjected to the human equation which we all know can become distorted or even corrupted and twisted.

In a case involving DNA the court is told of the facts and probable estimates of that DNA recurring in the population. In fingerprint cases they are told “That IS his fingerprints”, because that person reporting says it is.

It is possible to show the fingerprints on a screen, side by side each other, but you can also do the same with DNA profiles. Each still need to be explained to the court….

Both disciplines need to co-exist side by side. Each is not really 100% fool-proof is it?  And with life and death hanging on this thread as it does in so many countries such as the USA should we not take every opportunity to ensure we have the right person for the crime?

Let me know what you think of this in the comments.


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