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It's all in the bugs

Forensic DNA tests have become a standard part of police work all over the world. If you have watched any of the police shows you will have a good idea why DNA evidence is so important. If someone claims to have, ‘never been there before in my life…honest!’, and you find a sample of their DNA at the crime scene, you know there is definitely something fishy going on…

Crime scene

Contaminated samples

But things are not always as straight forward as they seem on television. One of the main problems is crime scene contamination. An average home will contain traces of genetic material from all the people that been there over many years. Just think of all the people who have visited your house, quite a lot right! Or imagine all the hundreds of school children who have sat in the same seat as you over the years. Just think, your seat is contaminated with hundred of strands of DNA from other people! How could scientists find your DNA out of such a huge mixture? This is a very tricky problem to solve.

Isolating DNA

That’s just what a team of scientists have been trying to do. Imagine how useful this could be? It would help forensic scientists easily solve crimes. It could also help them solve many old crimes. As long as they still have the DNA samples from old cases, they could use the new technology to isolate DNA.

How do they do it now?

At the moment police forensic experts struggle to identify a person if the sample contains less than 10 per cent genomic DNA. A standard DNA tests takes between 24 and 72 hours, but only costs a few pounds. The results are compared to samples of known DNA on a criminal database. The problem is that by the time police get the results from the DNA test, the suspect has usually been released. Ideally, it would be better to get the tests back much faster.

Could there be a faster way to test DNA?

Yes. A group of scientists have a developed a machine that can copy, amplify and analyze DNA samples very quickly. And it can find individual DNA, even if it is mixed with lot of other people’s.

All that is needed is a cotton swab of the inside of a suspect’s mouth. This swab collects cheek cells. The DNA is then extracted from the cells with the help of a few chemicals and some heat. It is then placed on a chip that does the analysis. The whole process only takes about four hours. Eventually scientists hope it will only take two hours. This is great news for the police, but bad news for criminals!

Taking a DNA sample

Better than DNA and fingerprinting?

Forensic scientists have come up with a new way to identify people. Not human DNA or fingerprints, but bugs! Yes, bugs! All of us have a mix of skin bacteria that is unique to us. Every time you pick something up you leave a tell-tale trail behind.

Microscopic organisms live on your hands

Let’s say you used someone else’s keyboard to send an email, but then you wiped the surface so that your DNA and finger prints disappeared. Scientists can now look at the bacteria left behind on the keyboard and match it to you. Again, very good news for the police, but very, very bad news for criminals.

The project is still in its early stages, but one day police might be testing for bugs (yuck!) as well as DNA and fingerprints.

Did you know?

What is genomic DNA?

This is the DNA that writes our genetic traits. This includes things like the size of our earlobes, if we have dimples or if we can roll our tongue. This is the DNA that forensic scientists use to find out someone’s identity.

The big questions:

How do you find out if a suspect has visited a crime scene?

How can you sort out the suspect’s DNA from all the rest?

How do you get a DNA sample analyzed before the suspect is released?

How can you tell a person has been there even without DNA or fingerprint samples?