Forensic science lab 4.4 What equipment do forensic scientists use to assess evidence?

I’m Dave Jones and I’m the chief Scientific Officer at Cardiff’s central Police Station. A recent murder in Cardiff Bay near the docks has generated a lot of evidence and I need to organise an assessment of it in time for a court appearance next week. Let me give you a tour of my lab so you can see the sort of things we have to do.

Simple cards with chemicals bound to their surface are used for a quick check on the blood groups of victims, suspects and even blood stains found at the scene. This is one of the first tests we do – mainly to rule out suspects so that we do not do expensive DNA fingerprint tests. They cost about £1000 and would soon use up our budget if we tested everything.

This is our DNA fingerprint machine. It is so sensitive we can get a DNA fingerprint from a stain that is almost too small to see. And it’s not just for blood. We can get DNA from cigarette ends if someone has put it in their mouth and from semen and other body fluids in rape cases. I’ve had some evidence sent through from the murder scene and we’ll be using this machine this afternoon.

We get through hundreds of fingerprints in a week. We use different techniques for different surfaces. An empty glass used by a suspect will give some excellent prints using powder. Fabrics can produce clear prints too if we use magnetic powder or special fluorescent dyes. We scan all prints into a computer for almost instant checking against the millions of prints we hold on record. If the Cardiff Bay villain has left any prints we should find a name in seconds.

This microscope is fitted with a camera so that we can take photographs of tiny samples of pollen and dust or even fragments of hair. We can match the pollen to particular plant types so we can tell if someone was in a particular area. We can identify a villain's hair quite easily – just a centimetre of hair and we’ve got the criminal.

This is a high quality camera which we take to the crime scene so that I can record evidence without having to bring it back to the lab. This is good for footprints, tyre tracks and even the particular pattern a knife or metal blade makes when it cuts through wood or fabric. Digital cameras are also used so that I can upload pictures straight onto a computer and see them quickly.

We usually take casts of footprints and tyre tracks as well. These are taken back to the lab and examined under a low-power microscope. Even tiny marks on a tyre can be enough to give away the fact that a particular car was present at a crime. Checking tyre tracks and footprints has to be done carefully, so the smallest details can be picked up. They can be the evidence that solves a case.

Every gun has marks inside the barrel known as rifling. When the bullet is fired it is scratched by these marks. We can match these marks on the bullet to the gun it came from. We fire the gun in a special room, collect the bullet and then compare it with the one from the crime.

Evidence needs to be handled very carefully. Can you explain why we have to follow these rules? Evidence-handling procedures 1All evidence must be signed in by Chief Officer prior to analysis. 2All officers must provide DNA samples and fingerprints prior to working in the laboratory. 3Appropriate disposable protective clothing must be worn when handling evidence and destroyed after one use. 4No evidence to be disposed of without written permission from the Chief Officer.