Det Supt Steve Fulcher was led by Christopher Halliwell to the body of Becky Godden in 2011
A detective who did not follow arrest guidelines in a double murder case has been found guilty of gross misconduct, the BBC has learned.
Det Supt Steve Fulcher did not read Christopher Halliwell his rights before the former taxi driver led him to the body of Becky Godden in 2011.
As a result, Halliwell was never charged over her death.
In October 2012, Halliwell was jailed for life for the murder of 22-year-old Sian O'Callaghan.
Mr Fulcher was brought before the formal misconduct hearing after an inquiry by the Independent Police Complaints Commission (IPCC).
The IPCC found Mr Fulcher had breached the Police and Criminal Evidence Act (Pace) and it recommended Wiltshire Police should consider a charge of gross misconduct against Mr Fulcher.
The hearing is due to continue tomorrow.
Miss Godden was last seen alive by a police officer in Swindon in December 2002.
Halliwell led police to her body in a shallow grave in Eastleach, near Cirencester, Gloucestershire, in 2011, shortly after he confessed to killing 22-year-old Miss O'Callaghan, from Swindon.
Becky Godden's body was found during the
search for Sian O'Callaghan
In October 2012 the former taxi driver was jailed for life for Miss O'Callaghan's murder.
However, a High Court judge ruled his confessions over Miss Godden were inadmissible, as there had been "wholesale and irretrievable breaches" of the Police and Criminal Evidence Act (Pace) guidelines.
Under Pace rules, which govern the questioning of suspects, Halliwell should have been cautioned several times during cross-examination.
But during a court hearing in 2012, Mr Fulcher, who advised officers across the country on how to conduct murder investigations, admitted he had not "considered it".
He added: "I believed that again, the right thing to do was take the information he was prepared to give, but I accept he was not cautioned at that time."
Mr Fulcher also admitted during cross-examination that he had become "frustrated" that Halliwell had refused to answer any more questions, having finally spoken to a solicitor.
"I thought it was utterly ridiculous that someone would take me, 12 other people and a surveillance helicopter to the deposition site of two bodies and then seek to find some loophole or quirk in the law to get away from the fact he was a multiple murderer," he said.