The burglars of Birmingham all wear Nike Air Max trainers. Within minutes of being called to a domestic break-in in the north of the city, Nick Parker, a forensic scene investigator, has dusted down the floor with magnesium powder and identified two sets of offending footprints. “You need fashionable footwear to burgle people’s houses,” he says wryly, crouched uncomfortably between the dining table, dresser and patio doors as he brushes away excess powder to sharpen the image. Soon, the characteristic pattern of squares emerges across the sole, together with a bow-shaped curve separating the ball of the foot from the heel. Parker knows that the criminals he tracks are particular about their appearance. When he’s called upon to confiscate suspects’ clothing, “it’s rare that you don’t open the wardrobe and see row after row of designer brands,” he says.

Parker, who started his career in the military, could not be more different from the ostentatiously fashionable criminals he describes. He has spent the past 23 years examining crime scenes and, like all investigators at West Midlands Police, wears a simple uniform of dark fleece, dark trousers and sturdy lace-up leather boots. FSIs, as they are known, find out what they’ll be doing the next day from watching the news the night before. As civilian police staff, they arrive at the scene only after warranted officers, paramedics and fire service personnel have torn through it, making arrests, dousing flames and tending to stricken bodies. Entering this aftermath, the investigators work with senior detectives to decide what evidence they need, before dusting, lifting, swabbing and photographing the traces left behind by offenders.

But in recent years, forensics has been forced out of the shadows. High-profile successes, such as the discovery of new DNA evidence in the murder of black London teenager Stephen Lawrence, have ­enabled historic convictions. At the same time, the profession — its profile raised by TV programmes such as Silent Witness and US equivalents CSI and NCIS — is facing a host of new difficulties. Forensics teams have suffered a disproportionate share of government cuts to police funding. Admittedly, dramatic falls in burglary and vehicle theft over the past decade have meant fewer crime scenes for FSIs to attend. However, these have been offset by sharp rises in online fraud and cyber crime, which demand new skills in digital analysis and preserving evidence from phones, tablets and laptops.

These rapid transitions have intensified the psychological and physical pressures of the job. On average, the 70 FSIs at West Midlands — the UK’s largest force after Scotland Yard — work on at least two murders a month, as well as countless assaults, drugs busts, arson attacks, terror arrests and bombings. Just before Christmas, a forensics team spent 12 days in the same house taking evidence for a murder case, breathing in air cloudy with fingerprint powder and pungent with decay. When schoolgirl Christina Edkins was stabbed to death on a bus two years ago, one investigator, who had a young daughter of his own, sat on the top deck with Christina’s body as the bus was driven to a secure forensics garage “so she would not be on her own”.

Decades into his career, Parker displays a calmness common across members of the profession. When asked what it takes to be an FSI, he reflects a moment, still hunched over his trainer prints by the patio doors. “You need good knees,” he says.

For all the advances in forensic science, some aspects are still reminiscent of the tactics deployed by Sherlock Holmes and other gentleman sleuths. In the laboratory at Ridgepoint House, the West Midlands forensic headquarters, senior technician Scott Richards oversees 11 staff who are experts in finding and treating fingerprints so they can be photographed, magnified and used in evidence. Last year, the team lifted prints from more than 25,000 separate exhibits including firearms, mobile phones, documents, broom handles, car doors, windowpanes, handcuffs, sex toys and fruit.

Their laboratory is a labyrinth of interlocking rooms, set out with lasers, lamps, microscopes and cameras. Richards, who has spent more than 20 years in forensics, delights in catching criminals who have been sloppy. “A lot of murders are crimes of passion and they’re not planned. And even when people think they’ve cleaned up really well, the question is, ‘Did you clean the bleach bottle?’” he asks jovially. “Oh yeah, I could carry out the perfect murder, for sure, that’s what I tell my wife,” he laughs. “I say, ‘No one would ever find me!’”

Nick Parker, West Midlands forensic scene investigator

The fingerprint detection process is simple but time-consuming and often fiddly. Porous materials such as paper and wood are treated with the chemical ninhydrin, which reacts with the amino acids in fingerprints, turning them purple. Non-porous materials such as plastics are put in a fume cabinet filled with vaporising superglue, which adheres to the prints, forming a white skin. These ghostly traces are then dyed neon-yellow to increase their visibility.

To Richards’ frustration, he and his team spend most of their time trying to extract prints from the worst possible surface, which is thin polythene. “Well over 70 per cent of what we get is bags — bin bags, carrier bags, dealer wraps, bags that have been wrapped around guns, bags that have been put over people’s heads,” he explains. “It’s a nightmare. I wish all drug wrappings were paper, it would make my life a lot easier.”

In contrast with plastic, paper is easy to treat, and the technicians recently succeeded in pulling usable prints from some documents that had been lying in a briefcase since the early 1990s. This led to a breakthrough in an ongoing fraud case. Positive identifications, known in forensic lingo as “idents”, make the hours spent at the glue cabinet or staring down a magnifying lens worthwhile.

“When it pops up on your screen, and the message says you’ve got an ident, it’s like, ‘Yes, come on. Go to jail and do not pass go. I’ve got you,’” says Richards, fist-pumping the air. “There’s that ­personal pride in doing what you do to catch these people.”

. . .

Becky Taylor, manager, West Midlands crime co‑ordination team

On serious investigations, finding what FSIs call the “golden nugget” of evidence which identifies the criminal can take months. Several floors above the fingerprint lab, an elite team of experienced investigators work as crime scene co-ordinators, liaising with detectives to oversee the forensics on major crimes such as murders, rapes and arson attacks.

Becky Taylor manages the team of 13, reduced from 35 when budget cuts were imposed two years ago. She describes the job as “body after body after body, pretty much most weeks”.

“The worst we’ve had was end of June, beginning of July . . . when we had six murders in addition to a couple of suspicious deaths,” she remembers. “The workload can be very intense, very challenging.”

Unperturbed by the subject matter, the co-ordinators, a tightly knit team, reminisce about their most cunning breakthroughs. Andy Nixon, a forensics veteran who speaks in an Irish brogue, recalls a man who was found dead in his bathroom three days after being assaulted in a pub. There was no forensic evidence but eventually a colleague, Rob, suggested treating the victim’s coat in the superglue cabinet. This exposed a footprint which was enhanced with lasers and lights, producing a green fluorescent Adidas logo. Rob happened to know that Guinness fluoresced green under a UV light.

“Who would have thought of that?” asks Nixon. “But it worked because the man [the suspect] had been in a pub and had obviously stepped in some Guinness and kicked this man when he was down on the ground. So of course we then compared that to the suspect’s shoes. That was really out-of-the-box thinking on Rob’s behalf.”

Steve Priest, who has been in the job for nearly three decades, was initially stumped by the case of an 80-year-old woman who had been raped and murdered in her home. The police had no leads and the scene appeared to have been well cleaned, but Priest suddenly decided to check for fingerprints on the headboard of the bed, which yielded a match on the national print database. “That’s probably one of my favourites, if you like, for want of a better word,” he says.

Scott Richards, senior technician, West Midlands forensic laboratory

Dealing with such cases is harrowing. The co-ordinators used to have mandatory counselling sessions every six months but these stopped abruptly after there was a “bit of a reduction in occupational health”. Taylor admits the job is “not for everyone” and that you have to be a “special kind of person” to deal with the operational side. Given the macho culture that often prevails in serious crime work, Taylor is surprisingly honest about her apprehensions. “I’ll put my hands up and say I’m not a big fan of dead people,” she says.

While Taylor found the counselling helpful, her colleagues are more blasé. Nixon says he can be working on a decapitated head on a postmortem bench and just “looking at what forensics I can get from it”. Priest concurs that he “loves” taking the photographs at postmortems because “you get up quite close and . . . you’re thinking, have I got everything that I need at the angle that I need, is it lit properly?”

The team agrees, however, that the support of colleagues is the best protection against long-term trauma. “Nobody else understands what you’ve seen or smelt or breathed in apart from the people in this office,” Nixon says. “And there is a little bit of humour involved as well . . . It’s not disrespectful but it does help.”

Hidden at the back of a quiet industrial estate in Tamworth, northeast of Birmingham, the private lab where West Midlands sends its samples for analysis has an altogether more clinical atmosphere. In the vast unmarked building, DNA is extracted, blood-splatter patterns scrutinised, glass fragments identified and clothing fibres magnified. Technicians in white bodysuits and masks examine evidence on benches protected with several layers of brown paper. Security around the labs is tight and visitors to the centre must supply DNA swabs so they can be excluded in the event of contamination. Anyone whose shoes or clothing has come into recent contact with gun residues is banned.

LGC, which runs the Tamworth lab and four others around the UK, received just under £2m to provide forensic testing for West Midlands in the past financial year, having absorbed much of the work previously carried out by the government-owned Forensic Science Service. The closure of the FSS in 2012 sparked a lucrative spell for LGC, which has increased its turnover by 70 per cent to £220m, and boosted its staff from 1,400 to 2,000 in five years. Now owned by the private equity firm Bridgepoint, it has attracted the attention of chancellor George Osborne, who praised its export growth and job creation on a visit to the London laboratory in January. As well as fulfilling contracts for UK police and military, LGC also serves overseas clients including the Royal Gibraltar Police and law enforcement teams in Trinidad and Tobago.

It’s rare that you don’t open the [suspect’s] wardrobe and see rows of designer brands

The increased workload has brought some high-profile successes. It was LGC scientists who discovered new evidence which helped convict the killers of Stephen Lawrence, ending two decades of failed prosecutions. During a cold case review, analysts managed to trace microscopic threads of Lawrence’s red polo shirt on a sweatshirt and jacket belonging to two of the suspects. The final breakthrough came when a minuscule spot of blood on the jacket, identified through high-level magnification, was found to match Lawrence’s DNA.

There have also been embarrassing lapses, however. Three years ago, the company had to apologise to the family of GCHQ codebreaker Gareth Williams, found dead in his flat inside a holdall, after it emerged that a typographical error in the DNA data had led to Scotland Yard spending more than a year trying to trace a non-existent suspect.

Inevitably, the closure of the FSS has proved controversial. Earlier this month, the National Audit Office warned of a risk that standards would slip following the transfer of work to companies and in-house police labs and that, in the future, lack of forensics capacity could put trials in jeopardy. Becky Taylor, of the West Midlands crime co-ordination team, spent two years at the FSS before joining the police. She fears that commercial attitudes have eroded the previous culture of academic inquiry which led to advances in forensic science. Andy Nixon misses the discursive chats he used to have with FSS scientists, “going off on tangents” in the hope of finding a clever way around a problem. “[LGC] is not willing to discuss anything unless there’s money in it for them,” he says simply.

But Chris Sims, chief constable of West Midlands, and the lead officer for forensics provision across the country, rejects such criticisms. “I think there’s almost some mythology that’s grown up, that FSS was doing lots of research, that FSS was a public-facing, public organisation,” he says. “I think some of this is a slightly rose-tinted view of what the FSS was many years ago. By the time it had come to the end of its life, it was a commercial provider in exactly the same way as LGC and the others.”

Steve Priest, West Midlands crime scene co-ordinator

Far from retreating from the private sector, Sims — who believes in police forming “partnerships” with companies in order to meet austerity targets — looks forward to an expansion in its role. The chief constable says he would like to move from the current “commodity-based” model in which police forces buy a fixed number of tests into a “more mature” system where they are buying “a relationship and a service”. In particular, he suggests that digital forensics — where analysts must triage “megabyte after megabyte” of evidence — could be a growth area for forensics companies.

When pressed on what the future might look like, Sims describes a new contracting arrangement which “rewards innovation and improved service” as opposed to making blanket payments. Under this vision, companies such as LGC would be more likely to handle an entire case, from crime scene to conviction. “That is something that is under discussion,” he says. “I think it would be very positive.”

. . .

At the West Midlands forensic headquarters, FSIs also have reasons for optimism. Over the past few years, digitisation has streamlined their systems, speeding up identifications. Inked fingerprint forms no longer need to be kept in vast physical libraries; print identifications, which used to take weeks, are now turned around in 24 hours. The force is testing new technology which will speed up DNA matches from the current week-long wait to a one or two-day service. Thanks to new software, crime scene photographs can be mapped on to a 3D reconstruction of the relevant house or building, allowing investigators and juries to retrace events as they happened. The growing footwear-identification team is honing its skills, adding daily to the 20,000 items currently listed on the national database. They specialise in the most common Nike and Adidas trainers but are also branching into flip-flops to get a better handle on the casual summer thief.

As the afternoon shift wears on, Nick Parker gets ready to leave the scene of the burglary in north Birmingham. He lifts the silver-powdered impressions of the perpetrators’ Nike Air Maxes on to sticky acetate, labels them and files them into evidence bags. He advises the house-owners about buying safer locks for their patio doors and installing an alarm — although he admits this might be set off by the family’s elderly dog, which slept though the nocturnal intrusion. He packs up his black plastic toolkit — the paper bags for confiscated clothing, torch, putty, brushes and factsheets on identifying bones. Then Parker gets into his black van and is on the road again, to the next crime scene and the haul of evidence still waiting to be uncovered.

Helen Warrell is the FT’s public policy correspondent

Photographs: Rob Ball