IT was the vital piece of evidence that helped snare a killer.

A photo fit image showing the likely face of a woman whose dismembered body had been found on Corstorphine Hill in Edinburgh finally led police to identify the remains.

The victim was Philomena Dunleavy, 66, from Dublin. She had been killed by her son in late April but her mutilated corpse had lain undiscovered until June 7.

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For weeks police tried in vain to discover who the woman was, with appeals focusing on her "distinctive rings" - including a traditional Irish Claddagh ring.

The high-profile campaign, which featured on the BBC ­Crimewatch programme, drew a blank until July 1, when the crucial breakthrough came in the form of a facial reconstruction.

The image was immediately recognised by one of Mrs Dunleavy's relatives in Ireland and on July 10 James "Seamus" Dunleavy was charged with his mother's murder.

The expert who produced the photo fit said the case was the most significant she had worked on in Scotland.

Professor Caroline Wilkinson, 48, of Dundee University, who specialises in craniofacial ­identification, had previously created the facial depiction of so-called "King in the car park" Richard III and, more recently, brought the face of Mary, Queen of Scots to life for the National Museum of Scotland.

Last summer, she was called in by police to create a likeness of the mystery victim based on her skull.

Ms Wilkinson said: "It is always good for us when we get an ­identification quickly, because it means we've been very useful. It's exciting to be able to see the results quite quickly.

"I would tend to look and say, 'the eyebrows aren't right, the hair's a bit wrong', but at the end of the day it's a pretty good likeness. What's important is that someone has been prompted to put a name forward.

"From an academic point of view we'd like it to be perfect every time, but it never is."

Craniofacial identification tends to be used in difficult ­investigations, such as in cold cases or where the body has been hidden, as in this instance. Police investigations make up a large part of the work carried out by Ms Wilkinson and her team and she has worked on cases all over the UK and Europe.

She said it was not usual to be able ultimately to compare pictures of how a person actually looked to the image she had produced

"Something like 60% of cases we have been involved in have led to an identification, but that is not always because of the ­reconstruction," she said.

"We have done our own lab tests with living people, imaging their skulls and then reproducing their appearance in some way. That allows us to measure how accurate we are."

The work involves taking a 3D model from a scan of the skull into a computer.

Muscles are then imported from a database and altered to fit, before other soft tissue and skin is added according to the age, sex and ethnicity of the person, if it can be established by forensic anthropologists.

Measurements are taken of anatomical features such as teeth, eye orbitals and the nose aperture to give information about how they should look. The team have established standards they can use to help them produce the most likely appearance for these features.

The individual's gender can normally be determined from the skull in adults, though not in children.

Ms Wilkinson said: "The most difficult things to work out are skin colour, eye colour, whether someone had wrinkles or how fat or thin they were."