Have you seen this 'Angel'?

The bones of the girl, who police have nicknamed "Angel", were discovered in Belanglo by a group of trail bike riders in August last year, and police have still been unable to determine her identity.

They also have little idea how long the remains have lain in the forest, saying she could have been killed anywhere between six months and 10 years ago.

Angel is believed to be anywhere between 13 and 25 years.

A reconstruction of what Angel might look like

The girl has never been reported missing, dental examinations have not determined a match, and no one has yet come forward to accurately identify her.

In the hope of sparking the memory of witnesses, friends, or family, police have now issued a likeness of the girl's face.

The image was created by forensic analysis of the skull by a facial anthropologist from the University of Western Australia.

NSW Homicide Squad Commander Detective Superintendent Michael Willing said,

"We're hoping someone might remember her as being a friend or a neighbour, or even someone they recognise as having been a member of their local community."

Police also found a short sleeved T-shirt with the word "Angelic" written in distinctive pink text, with a rose, and a heart with angel wings.

So what is known about Angel is this:

* She was between 13 and 25 when she died.

* Her bones could have been in the forest for six months to 10 years and that was when she was believed to have died.

* Her teeth showed "signs of dental work typical of Western dentistry", but no matching dental records have been found.

* She had shoulder-length hair, although investigators do not know the hairstyle.

* A short-sleeved T-shift with the word "Angelic" in pink text, a rose and a heart with wings was found near her bones.

* An anklet sock, a shoelace and an earring were also found with the remains.

* Her remains showed signs of injuries, but investigators were not revealing what they were at this time.

* Investigators are treating her death as "suspicious".

"If we receive information to point us in the direction of who she might be, we would be in a position to confirm her identity through dental records," Detective Superintendent Willing said.

Last year, forensic testing ruled out the likelihood the girl or woman was a possible victim of serial killer Ivan Milat.

Milat was sentenced in 1996 to seven life sentences for killing seven backpackers - aged 19 to 22 - between 1989 and 1992.

How 'facial approximation' is done

Dr Hayes, who specialises in skull and soft tissue, said what was most important was that the image might trigger a memory in someone who knew Angel.

"The whole time you are working on it you are very aware that she's got friends and she's got family,'' she said.

"You are aware that this is someone who needs to be put to rest.''

Dr Hayes said the remains on such cases were usually worked on by a range of scientists - from forensic odontologists to facial anthropologists.

Dr Hayes starts the "facial approximation'' process by photographing the skull. The images are loaded into a powerful graphics program, which allows her to work at a high magnification.

The next step, which is key, is anthropometry - the measurements of a human body.

"What you don't see on television is all the measurements,'' she said.

"You don't see the excel spreadsheets, you don't see the stack of academic journals that you've got to go through for each different person. You don't see the double-checking.''

The next step is applying the measurements and data onto the image. Virtual soft tissues are attached to the image, and then the final surface of the face is created.

But Dr Hayes said that such images should always been seen as approximates.

"You are imposing averages. Everybody is so unique and averages are averages. And no one is average.

"Anybody seeing the image should see it as a likeness.''

Anyone with information should contact Crime Stoppers on 1800 333 000.