In the US, the Innocence Project has freed 260 people imprisoned for crimes they did not commit – and inspired a new film starring Hilary Swank. In the UK the work is just beginning, but the lawyers who only take the most desperate cases of injustice have a first victory in their sights...

It was, in the words of the judge presiding over the case, a "brutal and undignified death". A 79-year-old woman, Joan Albert, had been stabbed in a sudden, savage and brutal attack, her body found in the hallway of her Suffolk home on 16 December 2001. The pensioner had, police believed, been murdered during a burglary that had gone wrong.

Following months of investigations and forensic tests, the man charged with the murder was a 25-year-old office worker named Simon Hall. Hall claimed he was innocent: on the night of the murder he had been out drinking seven miles from Albert's home and he had no motive to kill the pensioner. The main evidence against Hall was a statement given by the prosecution expert, who claimed that black nylon flock fibres and green polyester fibres found in addresses and vehicles related to Simon Hall were "indistinguishable" from those found at the crime scene and on Joan Albert's body.

Despite the fact that all the other evidence pointed to Hall's innocence, including hairs and fingerprints found at the crime scene which did not match and his strong alibi, Simon Hall was sentenced to life imprisonment in April 2003. "Why you chose, in the small hours," Mrs Justice Rafferty told Hall, "to break into her home and stab her to death may never be known." The judge assumed, of course, that he was guilty.

A dark and rainy late afternoon in December, and in a café opposite the Royal Courts of Justice in London I meet Dr Michael Naughton. He is a fast-talking man in his late 40s, a former machine-shop foreman and mechanical engineer from a large Irish Catholic family. When an industrial injury forced him to change careers Naughton studied criminology and became interested in miscarriages of justice. "Coming from my background, I'd had experience of the criminal justice system," he says. "Then I started meeting members of the Birmingham Six, and the shared connection of our biographies made a huge impact. What started as a theoretical interest suddenly became very personal."

In 2004 Naughton, who was by then a lecturer in law and sociology at the University of Bristol, set up a British arm of the Innocence Project. The concept was new to this country, but in the United States it is an established feature on the legal landscape. The first Innocence Project was established in 1992 in New York by Barry Scheck and Peter Neufeld and, since then, due to their work, more than 260 people who had previously been convicted of serious crimes have been exonerated across the country.

"I established the project partly because I was getting dozens of letters from prisoners who were claiming they were innocent," Naughton explains, "and they wanted help to overturn their wrongful convictions." The aim of the Innocence Project was to undertake thorough and objective investigation – done by law students under suitable guidance – into alleged wrongful convictions of prisoners who have exhausted the normal appeals process and do not qualify for legal aid.

The work of the Innocence Project is about to become much better known. One of their greatest successes, the case of Kenneth "Kenny" Waters, who was convicted of murder in 1983 and spent 18 years in prison for a crime he did not commit, is retold in a new film, Conviction, which is released this month. The film details how Waters's sister, Betty Anne (played by Hilary Swank), put herself through college and law school, and helped clear her brother with the assistance of Innocence Project lawyers.

Following Naughton's example, there are now around 30 Innocence Projects in the UK, which are based in the law departments of universities. Although less established than in the US, British Innocence Projects work on the same principles: both networks use law students to work on cases, both only work on claims of factual innocence and both focus on serious offences such as rape and murder. There are currently more than 500 students, staff and pro-bono lawyers working on the cases of around 100 long-term prisoners. One of those is Simon Hall.

Simon Hall always maintained that he did not murder Joan Albert. He had witness statements that detailed his movements on 15 and 16 December; according to the police the murder was the result of a burglary that had gone wrong, but nothing had been taken from the house and, anyway, why would he break into a house between 5.30 and 6.30am when he could as easily have chosen an earlier time when any occupants were likely to be asleep?

The critical evidence that had convicted him had been fibres from a pair of black trousers, in his car and in a cupboard at his parents' home, which the prosecution's forensic expert said at the time linked him to the murder.

"When the Innocence Project was asked to assist in Hall's case, our first impression was that this was a highly unusual case," says Gabe Tan, the assistant director of the Bristol University Innocence Project, who began investigating the case. She found that although the fibres found on Hall might have been "indistinguishable" from those found on the deceased's body, "indistinguishable" did not mean the fibres were an exact match: it simply meant the fibres could not be distinguished utilising the specific technique applied by the Forensic Science Service at the time.

"The more we researched, the more concerns grew," continues Tan. "We learned that the fibres are easily transferable and susceptible to contamination, that they were not collected from Hall's addresses until six months after the murder." As a result of their investigation, Hall had his case referred back to the Court of Appeal, and it is while attending the hearings at the Royal Courts of Justice that I meet Naughton and Tan. The judgment on whether he will have his conviction quashed is announced this month. If Hall is freed, it will be the first time that the Innocence Project will have succeeded in overturning a conviction in six years of existence.

Is Naughton disappointed that the project has not been as successful as their American counterpart? "The Hall case is the first to go back to the Court of Appeal," he replies. "In the US it takes around six years to get a case overturned, and on cases which are not DNA evidence-based it can take anything up to 10 to 12 years. It took us four years to get the first case into the CCRC [Criminal Cases Review Commission], and we now have eight cases under review. If Hall is released, I believe it will create some momentum, and there will be more cases being reviewed and convictions overturned."

One of the key differences between the Innocence Project in Britain and the United States is that the majority of projects in the US only take on cases that could potentially be overturned through DNA testing. "In Britain the vast majority of cases we are dealing with will not be 'fortunate' enough to have their innocence established through DNA," Naughton explains. "Either because samples have been lost or destroyed, or DNA testing had already been carried out during the original investigation and did not yield results that could firmly establish the prisoner's guilt or innocence."

A typical investigation might include looking for possible alibis, conducting research into the reliability of evidence, and tracing and speaking to witnesses to help establish the validity of a claim of innocence. "If anyone contacts us and says they should not be in prison, we ask for a narrative of innocence," Naughton says. "We ask that they explain why we should believe they are innocent. We want them to tell us their story."

The Innocence Project at Bristol receives around 15 letters every week and it has corresponded with more than 800 prisoners in the past five years. It only works on cases of prisoners maintaining innocence who have exhausted the normal appeals process and do not qualify for legal aid. "We believe in letting the legal system do its job," says Naughton, "and only step in when the legal system can no longer assist an alleged victim of wrongful conviction."

Once a case is taken on, Naughton and Tan work with a team of law students who meet in the seminar rooms next to the Innocence Project offices for meetings and casework. Patrick Ormerod is a second-year law student at Bristol University; his interest in miscarriages of justice partly stems from his own personal experience of the criminal justice system. "On 31 January 2008 I was wrongly arrested for assaulting a police officer and received a caution," he explains. "It wasn't a huge miscarriage of justice in the grand scheme of things, but spending just one night in a cell when I knew I'd done nothing wrong filled me with anger and helplessness. A friend was prosecuted over the same incident. That incident made me realise that when the police have the power to do pretty much whatever they want, miscarriages of justice must be more common than you'd think. So I realised these are the people I want to help."

Ormerod, who wants one day to be a criminal defence and international human-rights barrister, and his fellow law students usually meet on Wednesday afternoons for five hours to work on cases. The students do specific tasks, including keeping track of current applications at the CCRC, tabulating and going through witness statements, and undertaking research on specific issues. "The work students do can enable a key piece of information to become apparent," says Lucy Edwards, another law student who works with the Innocence Project. "Even if the hours I put in only help a little bit, it's worth it."

What is interesting about these young students is they are under no illusions about the criminal justice system – both Ormerod and Edwards believe there are hundreds of innocent people in prison. The implication is that the role and need for Innocence Projects in Britain is set to increase. "They will take the strain of investigating miscarriages of justice that were once taken on by the CCRC," says John Cooper, a visiting professor in law at Cardiff University, "for both funding reasons and the fact that the CCRC are becoming less inclined to take cases on."

If Simon Hall's conviction is overturned it will be a milestone in the history of the Innocence Project in Britain and it will inevitably spotlight the campaigning work that the projects have been doing for the past six years; some day it may even spawn a film. For the founder of Britain's Innocence Project, his work is less of a job and more of a crusade; it is also a mission that gives his own life a meaning it may have lacked. "The criminal justice system does not allow for the possibility that the courts sometimes get it wrong," Michael Naughton tells me, "but there has to be an allowance that some of those in prison are innocent. People think that miscarriages are a thing of the past, but the sad truth is that they're not."

Conviction opens on 14 January. Visit innocencenetwork.org.uk

Sarfraz Manzoor is a journalist, author, broadcaster and regular contributor to The Observer