The Forensic Science Service likes to stay out of the limelight. Its offices have no logo or sign. Only a couple of police cars and a few smokers with lab coats hint at what goes on inside the iceberg of concrete and steel in London's Lambeth.
Yet this inconspicuous exterior belies the fact that this is the brain stem of policing in Britain, the place where some of the country's most important cases are broken down to their component parts and rigorously analysed by the 600 forensic scientists who work inside. And also the place where the ever-increasing number of students studying forensic science – 5,664 in 2009, up from 2,191 in 2003 (a rise researchers attribute to the popularity of the television series CSI) – hope to end up.
It was here the revolutionary DNA Database was born in 1995. The National Firearms Database, which provides police with an automated system for comparing firearms and ammunition recovered from crime scenes, is housed here. And, as my guide points out, it was in this building that scientists worked 24 hours a day, seven days a week after the 7/7 bombing, processing DNA.
Today though, I'm here to visit the "trace and marks" laboratory and observe the excruciatingly detailed procedure which forensic investigators carry out on foot, tyre and weapon marks left at crime scenes across Britain. And while I'm at it, get a taste of the type of work which forms the mainstay of a new documentary series called Forensic Investigators, which starts on CBS Reality tomorrow.
But I'm already a little underwhelmed. Reared on a diet of Silent Witness, I'm expecting an all-singing, all-dancing laboratory, complete with glossy-haired staff and eye-searing overhead lights. In fact, the L-shaped room is more Sherlock Holmes than CSI. "We're more like an A-level chemistry lab," says Dr Sarah Jacobs, a senior forensic scientist with 10 years experience, as she leans across appropriately school-like stained wood benches. "We only go out to crime scenes three or four times a year, as it's quite costly for the police. And if I was going out to a scene," she says, "I certainly wouldn't wear high heels."
Shoes, high-heeled or otherwise, are a professional obsession for Jacobs. What the FSS refers to as "Cinderella work" – matching shoe marks found at crime scenes with the shoes of suspects – takes up 75 per cent of her working week.
"My most recent case was the murder of a lady in Portsmouth. The police had no firm leads, just a shoe mark left at the scene and a list of 600 people who were in the area at the time. I took prints of the marks using a gelatine plate, which attracts the dirt left by a shoe's sole. I then compared the print to 600 pairs of trainers. Every shoe has different wear and tear marks, you see, it's like a fingerprint. In the end we found a match with her ex-partner."
Sometimes, though, bones and flesh take the place of shoes. In cases of fatal attacks with garden tools or knives, FSS scientists make casts of entry wounds and the abrasion marks left on bones. "This happens a lot with decapitations," says Jacobs.
In such cases, quick-set polymer resin is laid over the severed bone which, when removed, gives the "fingerprint" of the weapon used, different saws or knives having different manufacturing marks.
Jacobs points out that separation – if not quite aloofness – is essential to the task: "A good forensic scientist needs to be able to disconnect, but without denying the dignity of the person whose crime you're working on. Along with patience and probity, it's a fundamental of the job."