A FORMER senior detective who investigated a sex-worker’s murder believes two pieces of DNA evidence hold the key to finding her killer.

Max McLean - West Yorkshire Police’s longest serving Detective Chief Superintendent - retired in 2010 having never managed to solve the case of Rebecca Hall’s murder.

In his time as the force’s leading homicide detective from 1998, Mr McLean lead 80 cases, but it is only the death of the 19-year-old mother-of-one which remains unsolved.

Her badly beaten body was found in an alleyway behind a company car park in Thornton Street, Bradford, on April 26, 2001.

The teenager was missing from her home in Elizabeth Street, Little Horton, for two weeks before her body was found.

Mr McLean was put in charge of the investigation and has revealed that two pieces of clothing taken by forensic experts from Miss Hall’s body are vital to finding the killer.

Officers have tested the clothing many times, but there has been no clear DNA match because of their poor quality.

However, Mr McLean hopes advances in technology will mean the clothing can be tested further to snare the murderer.

He told the Telegraph & Argus: “The most important thing we have in Rebecca’s case is the potential for a scientific solution some day.

“Where I have some confidence in this case is we do hold material which may be capable of some further examination.

“I think there is potential we might be able to nick somebody, and in my view, those DNA samples could be from areas of her clothing which would require an explanation from anybody who had a match.

“That is the biggest opportunity in Rebecca’s case. The police do hold that and it will be retained.”

Although the evidence has been tested repeatedly, the results have never been able to prove who the DNA belonged to.

Mr McLean added: “The two DNA profiles raised were of poor quality, so therefore weren’t sufficiently strong to do normal searches on a database to say “it is Alex or it is Max”.

“The profiles would have matched thousands of people within the database.

“The profiles are not sufficiently discriminating, meaning they could say, ‘yes, Alex is one of the people who matches this, but so is Max and the person next to us.’

“It wasn’t sufficiently discriminating to say for certain ‘that is who it comes from’.

He also believes some of Miss Hall’s missing belongings could also prove crucial to cracking the case.

Police appealed for information at the time of the murder for anyone to come forward if they had seen a pair of black knee-length boots, a limited edition South Park watch and a Motorola StarTAC phone.

“Who remembers or who can put together her boots the South Park watch and the Motorola StarTAC phone?” added Mr McLean.

“Even after all this time there is someone in Bradford who can put all this together around that time.

“Somebody will know something about those items or will be able to put them together, will have seen somebody with those or heard them mentioned or talked about.

“I still think there is a potential there for somebody to come forward.

“All research will tell us that this is a single murderer, probably male, aged between 25 and 40.

“Did he remove them as trophies? Unless those items were left a little distance from Rebecca’s body then I guess they could have been picked up by somebody and taken.

“That’s possible, but one theory we have to work on is that, for some reason, the murderer took those things away.”

The gruesome murder shocked Bradford and left a son to grow up without his mother.

A huge poster campaign was launched between the police and Telegraph & Argus to appeal for information, and Mr McLean appeared on Crimewatch with Miss Hall’s mother.

Both appeals produced a number of tips, but the deaths of sex workers are notoriously difficult, as potential witnesses are often unwilling to be associated with prostitution, even if they have crucial information.

Mr McLean added: “We did raise a huge number of potential suspects, because sadly when you are talking about the murder of a sex worker, the potential for a suspect pool is huge.

“I do reflect on if we got close and if we interviewed Rebecca’s killer or if it was someone from left-field who we had never thought about or never suggested to us.

“I don’t know how close I came.

“When you are investigating the murder of a sex worker, you come across some very unsavoury characters and there were plenty of those.

“I feel confident the work of the enquiry team was carried out to a good standard and I would be surprised if we had interviewed her killer, but it is possible.

“Very few people want to come forward and help when you are dealing with the murder of a sex-worker because nobody wants to associate themselves with that trade.

“There’s the inherent difficulties of managing an investigation into the death of a sex-worker because it could be anyone.

“I have every confidence in the quality of the detectives currently in West Yorkshire Police who work within the Major Inquiry Review Team.

“I know they will be constantly reviewing the evidence.”

The teenager’s death raised a number of questions about why anyone would want to kill the young woman.

As far as the police were concerned, she was not involved in a gang, and could only have been seen as an easy target.

“You couldn’t imagine any circumstances in which she was targeted to be killed other than her being a sex worker,” Mr McLean explained.

“This isn’t some gangland feud and I would be surprised if it went beyond what she did as a sex worker.

“Somebody will know who killed Rebecca and you hope somebody is still aware of that.

“Before police eventually determine the identity of the killer, hopefully someone will come forward.

“On the very first night we found Rebecca we put certain people in Bradford under surveillance in order to try and understand their movements to see whether, now the body had been found, and it would be known it had been found, would they do anything unusual or different, but there was no evidence of that unfortunately.

“The investigation revealed an underworld in the Thornton Street area with the various types of people that were visiting there to participate in that kind of sex work.

During his final week as a detective, Mr McLean visited Miss Hall’s family with his successor and explained how the investigation will progress.

It is a case he still spends a lot of time thinking about and he is hopeful her family’s ordeal will one day be brought to an end.

“I want to get closure for them,” he added.

“She was so vulnerable there was no way she was part of any cartel or serious crime.

“Someone has selected her for her vulnerability and taken the opportunity to kill her, which is terribly sad.”

West Yorkshire Police declined to provide an update on the case when approached by the Telegraph & Argus.