POLICE evidence rules need to be looked at again, Karen Edwards said.

“It should continually be being looked at,” she told the Adver.

Killer Christopher Halliwell was not tried in 2011 for the murder of her daughter, Becky, after concerns were raised that the confession that led to the discovery of her remains was obtained illegally by police.

Lawyers said Det Supt Steve Fulcher had breached rules, known as PACE after the Police and Criminal Evidence Act, by not immediately taking Halliwell into custody after he had been arrested on suspicion of kidnapping Sian O’Callaghan.

Instead, the detective ordered officers to take the suspect to Barbury Castle, where the pair smoked cigarettes, After several hours Halliwell cracked – leading police to Sian’s body then asking an astonished Mr Fulcher if he wanted “another one”.

Halliwell had been cautioned twice already, but under the PACE rules Mr Fulcher should have done it again. The detective said he didn’t because he felt his suspect was about to lead him to Sian.

On the face of it, the decision seemed to pay off. Detectives had unmasked a serial killer. Halliwell was charged and Mr Fulcher was put forward for the Queen’s Policing Medal.

Longer term, it proved disastrous. The confession was ruled inadmissible, Mr Fulcher was investigated for gross misconduct and eventually left the police. It wasn’t until 2016 and Halliwell’s second trial – this time for Becky’s murder – that a judge said the evidence from that countryside confession could be heard in court.

Karen Edwards has always stood by Mr Fulcher – this summer describing him as a hero for finding her daughter’s remains.

She led a campaign for a change to the PACE rules, delivering a petition signed by more than 43,000 to Downing Street in late 2014.

Karen said then policing minister Damian Green had described PACE as a living document. A senior civil servant was said to have reviewed it at the time, but decided no changes needed to be made.

In 2018, revisions were made to PACE, tightening up the safeguards for vulnerable suspects.

Now, campaigner Karen has called for a further review: “Quite clearly there is need for change because it puts out police officers under huge stress.

“It should continually be being looked at.”