By Elaine Okyere
BBC News, London
Hands can distinguish one person from the next, but it is rare that a person's hand - and not their fingerprints - can lead to a conviction.
Freckles and blemishes on the male thumb were identical to Hardy's
For paedophile Dean Hardy, from south-east London, the distinctive freckles on his left thumb led to six years in jail.
The Metropolitan Police and forensic scientists discovered Hardy's blemishes matched those in a photo showing a man illegally touching a young girl.
The team behind the investigation have revealed that without the image of a face, it was a long process to get the evidence to secure a conviction.
Det Con Dave Adams, from the Met's child abuse investigation command, said: "In the last five years I have never had a case like it.
"We took photos of Hardy's hands while he was in custody and decided to see if it was the same person in the photos."
As an anatomist and forensic anthropologist Professor Sue Black studies the human body for a living and it was her research that led to the conviction of Hardy.
"When we look at someone it does not matter what part of a person it is, we look at them in a different way," said Professor Black, from the Centre for Anatomy and Human Identification at the University of Dundee.
Professor Black identified Hardy as a suspect through a process of elimination.
From looking at the photo the anatomist could tell that the perpetrator was a white, middle-aged man, but it was the discovery of an accident scar that led to a breakthrough.
She said: "We started looking at similarities and differences. We have all got scarring, but any scars from an accident are more useful for identification than a scar from surgery.
"Any hand that had the same surgery would have the same scar in the same place.
"If we find an accident scar we can build a 3D profile and the likelihood of this being two separate people becomes very slim."
At the centre, scientists look at forensic anthropology and analyse soft tissue and vein patterns to identify people. The centre also has a database of more than 2,900 images of fingers and hands.
Hardy was jailed for six years and could be banned from travelling abroad
"Our hands tell us so much about the way we live, a bricklayer will have very different hands from a surgeon," said Professor Black.
"We can try and conceal our age, but our hands and necks are areas you cannot not conceal."
After seeing the evidence against him Hardy admitted indecent assault and taking indecent photos.
The case has been hailed as the first of its kind.
However, Professor Black revealed the technology is now being used at a case in Edinburgh's High Court.
She said: "In the fight against crime we need an arsenal of tools.
"This technique will not replace things, but it means if all we have is a photo of a hand we can still tell something."