Taxi driver Christopher Halliwell is jailed for 25 years for murdering Sian O'Callaghan but will escape justice over second murder because of police blunder

He also confessed to police that he had killed drug addict Becky Godden-Edwards, but he will never stand trial for her death. Why? Because the police failed to follow procedure

Christopher Halliwell, 48, pleaded guilty to killing Sian O'Callaghan (right) but charges relating to the death of Becky Godden-Edwards were dropped (PA)

A taxi driver who abducted and killed a young clubber has escaped prosecution for the murder of a second victim despite confessing to police and leading them to the exact spot where she was buried.

Following his arrest for one murder, Chris Halliwell took police to two sites 30 miles apart where he had dumped the bodies of the young women in unconnected killings.

But major breaches of the rules governing the way police question suspects meant that he would stand trial for only one of them, it can be revealed.

The senior officer in the case, Detective Superintendent Steve Fulcher, has been suspended and faces an inquiry into his actions during the investigation. However the officer, a respected senior detective, yesterday received strong backing for his actions from the families of both women.

Taxi driver Halliwell, 48, was jailed for life yesterday at Bristol Crown Court after he admitted murdering Sian O'Callaghan, 22, in a sexually-motivated attack after picking her up outside a Swindon nightclub in March last year. He will serve a minimum of 25 years in prison.

The divorced father-of-three drove her to a remote forest where he stabbed her twice before dumping her body down a steep bank by the side of quiet rural road. The court heard that Halliwell then put missing posters of the young woman in the back of his taxi even as he tried to clear up traces of her blood inside.

He was arrested five days into the hunt but initially refused to tell police where he had dumped the body. He finally agreed after a nine-minute interview with Det Supt Fulcher, who took him to an isolated hilltop, accompanied only by a civilian note taker.

The killer then asked the astonished detective if he wanted "another one" and led him to another field in south Gloucestershire, some 30 miles away, where he had buried Rebecca Godden-Edwards, a drug addict last seen in 2002. Her family learned only ten years later that she was dead on what would have been her 29th birthday.

A judge ruled earlier this year that Halliwell would not stand trial for that killing because of "serious and irretrievable" breaches in the 1984 Police and Criminal Evidence Act governing the treatment of suspects that protects them from "oppressive" questioning.

Mrs Justice Cox found that Halliwell had been denied contact with a solicitor despite repeatedly asking for one in the four hours after his arrest.

He was finally taken to a police station and given legal representation, but has since refused to talk to police about the case.

However, outside the court yesterday, Ms Godden-Edwards' family said they "fully backed" the detective despite the collapse of the murder case. No forensic evidence was found on Ms Godden-Edwards' remains and the best chance of ever securing a conviction was if Halliwell confessed to another person, said Nick Hawkins, the chief crown prosecutor for Wessex. "We are very much in Mr Halliwell's hands if he wants to volunteer anything," he said.

Det Supt Fulcher is being investigated by the independent police watchdog and was suspended several weeks ago for "inappropriate contact" with the media during the case.

In a ringing endorsement of the officer, Ms O'Callaghan's father, Michael, told reporters: "I want to put on record the wonderful job that Steve Fulcher did finding our daughter so early."

Police are trawling through files to try to discover if Halliwell was responsible for any other killings. In the days after Ms O'Callaghan's killing, he told a colleague: "Who knows what or who you find buried out there. There could be lots of people over the years."

Two lives: the victims

Sian O'Callaghan

Ms O'Callaghan, 22, had just moved in with her boyfriend, Kevin Reape, when she was abducted and killed by Chris Halliwell. She had visited a number of Swindon nightspots with her friends. When she was reported missing the following morning by her worried partner, hundreds of people turned out to join the search.

Rebecca Godden-Edwards

A "beautiful and intelligent girl" whose life spiralled downwards into some "very dark places" after becoming addicted to drugs in her teenage years. Her family last saw her alive when she left the family home in 2001 after a conviction for burglary and theft to feed her habit. She told her family that she could not keep putting them through hell and would only return when she was clean. She never came back. Halliwell told police that he killed her at some point between 2003 and 2005.