CAREFULLY and gently, the cotton swab is run over the mysterious tiny wooden doll. Skilfully handled by the DNA expert, it is placed back into the equally small hand-carved coffin in which it was secreted on Arthur's Seat almost two centuries ago in the midst of an infamous killing spree.
Two serial killers were on the loose, their tally 17 murders. And it seems that in the midst of the horror, someone was secretly carving tiny effigies - one for each victim - and burying them quietly in a cave in the extinct volcano in the centre of Edinburgh.
The question is, who? And why?
It's a mystery that has remained until the 21st century, when Lothian-born forensics specialist Mike Barber finally got his hands on the so-called "murder dolls" to examine the theory that the person responsible for the tiny coffins and their contents was none other than one of the killers.
It's the latest twist in one of Edinburgh's oldest and most macabre murder cases which is being brought back into the spotlight in a new CSI-style drama documentary splicing reconstructions of the past with real-life present-day scientific investigation.
It is around 170 years since 17 minute figures in coffins were first found by schoolboys out rabbiting on Arthur's Seat back in 1836, prompting fears that they were related to witchcraft.
But it wasn't until the 1990s, decades after the dolls were bought and displayed at the Royal Museum of Scotland, that experts suggested that the 17 dolls in fact represented the 17 victims of the infamous Burke and Hare - murders for which Burke was hanged after Hare turned Queen's evidence to save his own life.
That work, by former National Museums of Scotland principal curator Allen Simpson and US academic Samuel Menefee, suggested that someone close to Burke and Hare made the figures and deposited them as surrogate burials out of a sense of compassion because they felt tainted by what they knew.
But after stumbling across a picture of the dolls while researching other mysterious deaths, TV producers working for the National Geographic Channel started exploring the idea that the man behind the dolls was in fact Burke himself in a bid to assuage his own guilt.
They approached Mr Barber, head of the specialist DNA unit at the Forensic Science Service in Wetherby, Yorkshire, to use his skills which are normally put to helping police solve modern crimes, to try and prove one way or the other whether Burke made the dolls.
The idea was that he should try and obtain a DNA profile from Burke's skeleton, which is kept under lock and key at Edinburgh University, and see if it matched samples taken from the dolls.
After growing up in Linlithgow, Mr Barber was very familiar with the exploits of Irish navvies William Burke and William Hare, who embarked on their notorious killing spree in the late 1820s to take advantage of a thriving trade in corpses for surgeons to hone their dissection skills. They became suppliers to Dr Robert Knox, at Surgeons Square, giving him bodies in return for money.
But Mr Barber had never heard of the murder dolls before. "It sounded really interesting, although I told them right from the start that the chances of us being able to find DNA linking Burke with the dolls were very, very small because DNA degrades over time and these dolls have also been handled by lots of people over the years leaving their DNA traces as well.
"And the museum wouldn't let us take the kind of samples which would be most likely to bring results because they would damage the dolls."
Initial work with the skeleton proved to be very exciting, however, as Mr Barber was able to get a partial DNA profile from the bone sample - enough to convict a modern-day killer if it was found at a crime scene. It took an entire day to get the DNA sample from the bone, using liquid nitrogen to freeze it to make it brittle enough to be ground into a fine powder.
The sample was then treated with a series of chemicals to extract and purify the DNA sample to get the best possible results. The final analysis was done almost "molecule by molecule".
"To get a profile on a sample as old as this is incredible. It's a great chance to see what the technology can do. Previously the oldest sample we had tested only went back about 40 years."
Unfortunately, the tests on the dolls found "absolutely nothing", as Mr Barber predicted. But, he says, they didn't disprove the theory, either. And after speaking to historians involved in the programme, Mr Barber for one believes that Burke probably did make the murder dolls.
He says: "I think it's pretty clear. The people I've spoken to during filming believe that it was Hare who was the real bad one and Burke was easily led and copped it when he was shopped by Hare."
The NMS bought the dolls in 1901 from a private collector, by which time only eight remained - the whereabouts of the rest is another mystery. Currently they are cared for by George Dalgleish, principal curator of Scottish history at the Royal Museum in Chambers Street.
Each one is about the size of an adult finger. The limited museum analysis to date - mainly simply observation plus analysis of threads from the clothing - dated the dolls to have been created around the time of the Burke and Hare murders.
It suggests that they were probably made from toy soldiers, while the coffins were probably hollowed from a block of Scots pine using a hooked knife like those wielded by cobblers.
While interested in the DNA work, Mr Dalgleish says the mystery, as ever, remains: "We still don't know what they are for and who made them. It's fascinating. There have been so many theories, none of which has been proved."
He is unconvinced by the idea that Burke made the figures, saying: "Yes, he showed all sorts of contrition - of course, he was trying to get off a death sentence. I don't think there is any evidence to suggest that these two men were anything other than cold-blooded murderers making a profit from killing people. They deliberately chose victims who they thought would not be missed.
"I believe the most credible theory is that they were made by someone who knew Burke and Hare, as suggested by Simpson and Menefee, but unless we find a contemporary document saying 'I did this', we will never know."
Meanwhile, Edinburgh University senior lecturer in anatomy, Dr Gordon Findlater, believes that despite the failure to prove or disprove the suggested link between Burke and the dolls, the findings could lead to more discoveries about Burke's grisly end.
He says: "Burke was not the most popular man. After he was hanged and his skin was removed during dissection some of it was used to make snuff pouches and wallets. There are so many artefacts around like that that are said to have been made from Burke's skin. It would be really interesting to take samples from them to see if they do match with the DNA profile from Burke's skeleton."
Lynn Child, executive producer with South African TV company Briteside, which made the programme for National Geographic, says: "The more we researched it, we found that it could have been Burke, or Hare, even Knox was a possibility. Knox also had a brother who worked with him, receiving the bodies. Only a limited number of people knew about the murders at the time. I see no reason why Burke could not have made the dolls."
Murder Dolls shows on the National Geographic Channel, on Monday at 9pm.
PARTNERS IN CRIME
THE crimes of William Burke and William Hare have fascinated people since the 19th century.
The Irish navvies came to Edinburgh to work on the construction of the Union Canal. Their murderous scheme was hatched in 1827, when one of Hare's lodgers, an old man named Donald, fell ill. Burke and Hare took his body from the coffin and took it to the anatomy offices of Professor Robert Knox and were paid seven pounds and ten shillings.
Their first murder victim, though, was a miller named Joseph, who they suffocated.
From then on, their victims ranged from sickly lodgers to old prostitutes. Their last murder was of a Mary Docherty, who lodged with Burke. She was discovered under the floorboards.
Burke and his partner Helen, and Hare and his partner Margaret were all arrested. But the police gave Hare immunity to testify against the Burkes.
Their trial began on Christmas Eve 1828 and on Christmas morning, Burke was found guilty and sentenced to death by hanging while Helen was freed. Burke confessed before he was executed, and Hare was released in February 1829.