Sian O'Callaghan

Justice Laura Cox ruled that Halliwell's confessions to killing each of the women were inadmissible as Evidence, as Detective Superintendent Stephen Fulcher had breached the guidelines of the Police and Criminal Evidence Act 1984 by failing to caution Halliwell and denying him access to a solicitor during the period that the confessions were obtained.

Sian Emma O'Callaghan (3 June 1988 – c. 19 March 2011) was a 22-year-old British woman who disappeared from Swindon, Wiltshire, England, having last been seen at a nightclub in the town in the early hours of 19 March 2011.

Her body was found on 24 March near Uffington in Oxfordshire.

She was last seen alive on Aylesbury Street in Swindon at 10:45pm on Friday 8 September 1995, at an area near the town's red-light district.

The body of Becky Godden-Edwards, 20, a woman who had been reported missing in 2007, was found after Halliwell's arrest; he had led police to the body.

At 02:52 on 19 March 2011, O'Callaghan was captured on CCTV leaving Swindon's Suju nightclub to walk 800 m to the flat that she shared with her boyfriend, Kevin Reape, in Swindon's Old Town area.

Reape sent O'Callaghan a text message at 03:24; analysis later showed that her mobile phone was in the Savernake Forest area, 12 mi away, at the time the message was received.

At 09:45, Reape contacted the police and reported O'Callaghan as missing.

On 20 March, the police issued their first public appeal for information, and announced that they had begun searching Savernake Forest.

They stated that the time that elapsed between O'Callaghan's appearance on the club's CCTV and her mobile phone signal (02:52 and 03:24 respectively) meant that the journey from Swindon to the forest could only have been made in a vehicle.

On 22 March, approximately 400 members of the public joined the police in their search of the forest.

The same day, an anonymous donor offered a £20,000 reward for information that would lead to finding O'Callaghan.

On 23 March, police announced that analysis of O'Callaghan's mobile phone signals led to the identification of a number of "hot spots" to be investigated.

Detective Superintendent Stephen Fulcher of Wiltshire Police said that the investigation was moving at a "rapid pace", and that "significant lines of inquiry" were being developed.

Members of the public were asked to stand down from searches.

On 24 March, police made an urgent appeal for witnesses of a green Toyota Avensis with taxi markings, which had been seen between Swindon and Savernake Forest shortly after O'Callaghan's disappearance.

On the afternoon of 24 March, police arrested a 47-year-old taxicab driver, Christopher Halliwell, from Swindon on suspicion of kidnapping.

The arrest was made at an Asda supermarket in north Swindon, where a green Toyota Avensis taxi was also seized.

Later the same day, O'Callaghan's body was found in a shallow grave near Uffington, Oxfordshire.

On 26 March the suspect was charged with O'Callaghan's murder.

During a news conference on 26 March, Fulcher stated that tests revealed O'Callaghan had not been sexually assaulted.

On 1 April, the inquest at Oxford coroner's court was told that it was likely O'Callaghan died from head injuries, though a forensic pathologist from the Home Office had yet to confirm a precise cause of death.

O'Callaghan's funeral was held at Kingsdown Crematorium on 18 April 2011.

On 19 October 2012, at Bristol Crown Court, Christopher Halliwell, 48, of Nythe, Swindon pleaded guilty to O'Callaghan's murder.

On 31 May 2012, taxi driver Christopher Halliwell appeared in court at a plea and case management hearing, and pleaded not guilty to the charge of murdering Sian O'Callaghan.

On 19 October 2012, he appeared at Bristol Crown Court and pleaded guilty to her murder.

He was sentenced to life imprisonment with a minimum tariff of 25 years.

The Court of Appeal upheld the sentence on 14 December 2012.

Following the guilty plea, it emerged that a second murder charge against Halliwell had been dropped as a result of an error in the police handling of the case.

On 23 April 2013, an inquest at Oxford Coroner's Court into the death of Godden-Edwards recorded a narrative verdict stating that the cause of her death, believed to have been in the final days of 2002 or early in 2003, was "unascertained but probably caused unlawfully by a third party".

In September 2013, the Independent Police Complaints Commission published the result of an investigation, which found that Fulcher had a case to answer for gross misconduct for breaches of the Police and Criminal Evidence Act and for ignoring force orders.

In January 2014, he was found guilty of gross misconduct and given a final written warning by a disciplinary tribunal.

In May 2014, Fulcher resigned from Wiltshire Police.

Karen Edwards, the mother of Becky Godden-Edwards, commented: "Had he have followed the guidelines, then Becky would never have been found, she would have never have come into the equation."

On 31 March 2016, Christopher Halliwell was charged with the murder of Godden-Edwards before magistrates in Chippenham, Wiltshire.

On 19 September 2016, a jury at Bristol Crown Court found him guilty of the murder after two hours of deliberation.

On 23 September, Justice John Griffith Williams sentenced Halliwell to life imprisonment with a whole life order for the murder, meaning he would serve his sentence without the possibility of parole.

In lead detective Stephen Fulcher's 2017 book on the O'Callaghan and Godden-Edwards cases, he wrote that after apprehending Halliwell he had ordered the re-opening of the investigation into the unsolved 1995 disappearance of prostitute Sally Ann John, believing he may have murdered her.

On 2 September 2019, ITV broadcast the first episode of A Confession, a six-part drama series based on the case, with Martin Freeman playing Detective Superintendent Fulcher and Joe Absolom playing Halliwell.

In September 2022, an investigation by the Independent Office for Police Conduct found that Wiltshire Police had missed significant opportunities between 2011 and 2014 to bring Halliwell to justice sooner for the murder.