By Duncan Staff
Director, BBC's One Life
A leading archaeologist has given up his gentle academic life in order to exhume bodies and use his skills in a different way - helping police solve murders and locating victims of the Srebrenica massacre in Bosnia.
Hunter works with anthropologists reassembling massacre victims
I try to fix the mask over my nose, but it keeps snagging on the viewfinder covering my right eye.
In the end I give up and try to block out the stench of decay by concentrating on what I am filming.
Two police officers in white boiler suits are digging a pit at my feet, directed by a balding, intense figure, the forensic archaeologist, Professor John Hunter.
"OK. That's layer 110. Bag it and tag it. Everything from here on in is the same layer as the body," says the professor.
The detective in charge of the murder case, Graham Pallister, crouches on the opposite side of the pit, muttering occasional instructions, as the dismembered remains of Mark Green are painstakingly uncovered. His reason for employing Professor Hunter is straightforward.
"A forensic archaeologist helps me find the body faster, and preserves evidence, so that it's harder for the perpetrator to get away with murder when the case comes to court," he says.
Relatives search for loved ones
But what drives Professor Hunter, an expert in the archaeology of the Western Isles of Scotland, to do such grim work?
"When you're practising traditional archaeology you're dealing with ancient times," he says. "The difference with forensic archaeology, which is usually about murder, is that you're making a real difference to people's lives."
It takes Hunter, his assistant Steve Litherland and the police 12 hours to expose the outline of the grave, half-section it and excavate. Every stage of the work is logged and photographed by scene-of-crime officers. Hunter's methods are slow, meticulous and scientific.
"I am tracing the killers' actions in reverse," he says. "The information gathered can help explain how the crime was planned and executed."
At around two in the morning, Steve Litherland bends and chips away at the red clay lining the bottom of the pit. Suddenly he stops, stands up, and turns to Hunter, squinting at the tip of his trowel.
"Yeah, that's skull," Hunter replies.
A year later, it emerges in court that Mark Green, an art lecturer, was beaten to death with a gas canister by Robert McMahon.
At trial, Hunter's evidence demonstrates that the grave was dug in a planned, meticulous manner and a defence of diminished responsibility is not viable.
Forensic work on remains found at Srebrenica is painstaking
The killer is sentenced to seven years and his brother James gets three years for helping dispose of the body.
Hunter began forensic work in the 1980s when he noticed how crude police techniques for finding and exhuming bodies were.
"I'd see TV pictures of men in boiler suits with spades and think: 'they must be losing a lot of evidence.'
"The fact is archaeology is all about the dead, and learning from their remains. It has got to be right to apply these skills in a way that makes a difference to the living."
Hunter has done around 90 police cases. But forensic archaeology is also being used to recover the victims of genocide, and prosecute their killers.
He has been working with the International Commission on Missing persons, in Bosnia, for the past five years. Their biggest task is to locate the 7,000 victims of the 1995 Srebrenica massacre.
The graves are becoming increasingly hard to find, he says, but the process is helped by his revolutionary new system.
His team begins by examining satellite pictures for signs of unusual vegetation - nettles grow a foot higher over bodies.
They then carry out a geophysical survey, passing electrical currents through the ground, to build up an exact picture of the grave before exhuming.
The bodies are reassembled by anthropologists, and their identities confirmed with DNA testing, before being returned to their families for burial in a new cemetery on the edge of Srebrenica.
When Hunter visits for the first time, thousands of green boards, bearing the names of men aged 15 to 70, protrude from the freshly dug earth. Families wander between them looking for husbands, brothers and sons.
"This is really quite numbing isn't it?" he says. "The scale and rawness of it all.
"But this is why we recover victims - to give them back to their families and to prevent their killers getting away with murder."
Professor Hunter's story is told on One Life, on BBC One at 2235 GMT on Tuesday 8 November.