Becky Godden's father angry at police for arrest mistake
"It seems to me, come to Swindon, commit a murder. You'll get away with it."
The body of John Godden's daughter Becky was found during the hunt for murdered office worker Sian O'Callaghan.
But killer taxi driver Christopher Halliwell, who led police to her buried body, will not face trial for her murder.
Charges were dropped after a judge ruled detectives ignored arrest guidelines.
It is a decision that has left Mr Godden not knowing definitively who killed his daughter after she went missing eight years ago.
"I'll never put my trust in the police again," he told the BBC.
"I'll go to my grave and not know who killed Rebecca Godden and I'll never forgive them for it. Never."
Halliwell was identified by police as the main suspect in 22-year-old Miss O'Callaghan's murder after CCTV caught him driving outside the nightclub in Swindon she went missing from.
But nobody realised the investigation would lead police to a second body.
Miss Godden's family were told of the discovery of her body on what would have been her 29th birthday.
Following Halliwell's arrest, he was taken not to a police station to be read his rights but to local beauty spot Barbury Castle by Det Supt Steve Fulcher.
The move was strongly criticised in court proceedings which the media were preventing from reporting until now.
Mrs Justice Cox said Det Supt Fulcher's decision to ignore guidelines in the Police and Criminal Evidence Act were "significant and substantial".
She added the move was intended to create "circumstances deliberately designed to persuade the defendant to speak".
And it meant that Halliwell would only face charges over the murder of Miss O'Callaghan and not Miss Godden, also known as Becky Godden-Edwards.
Det Supt Fulcher said he had made the decision to not take Halliwell to a police station in a bid to "appeal to the killer's conscience".
"Without his disclosure of Sian's location I don't believe there's very much likelihood of anybody finding her," he said.
But Mr Godden said the move was a "massive mistake".
"It's not right. It's not fair. Her life was taken illegally," he said.
"I've got to know whether he [Halliwell] did it or he didn't do it. That's what I've got to know.
"I'll never rest and I don't think the family will. We've got to fight for Becky. We've got to have peace of mind.
"Why should we pay this pain for somebody else's mistakes? I want closure, I want justice.
"I don't want this to become a cold case and for them to put it on the back burner."
Miss Godden's grandmother Miranda said her "world stopped" when she found out that the body had been found.
After the case against Halliwell collapsed she said "somebody has made a terrible mistake".
"They've got to pay, surely? Why charge him and then drop it?
"I was brought up to respect the law but [now] I've got no respect for them.
"Somebody dropped a big boo-boo, they really did, and somebody's got to pay."
The police and Crown Prosecution Service said the murder charge in relation to Miss Godden had not been dropped.
Det Ch Supt Kier Pritchard, head of protective services at Wiltshire Police, said that while the charge had never been put in court, "it is very much our intention to continue the live murder investigation and bring that final closure for Becky's family".
He said: "We will pursue all lines of inquiry we can and continue to provide support to the family.
"We recognise the last 18 months have been extremely distressing for the family and we are sorry for any anguish caused.
"We were able to recover Becky so she could be buried with the dignity she deserved, but the next step for us is to bring Becky's killer to justice."