Murder of Sian O'Callaghan
Sian Emma O'Callaghan (3 June 1988 –  March 2011) was a 22-year-old British woman who disappeared from Swindon, Wiltshire, 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 2011 near Uffington in Oxfordshire. On 19 October 2012, at Bristol Crown Court, Christopher Halliwell, 48, pleaded guilty to O'Callaghan's murder.

Timeline 

At 02:52 UTC on 19 March 2011, O'Callaghan was captured on CCTV leaving Swindon's Suju nightclub to walk  to the flat in Swindon's old town that she shared with her boyfriend, Kevin Reape. Reape sent O'Callaghan an SMS at 03:24; analysis later showed that her mobile phone was in the Savernake Forest area,  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 Steve 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.

Arrest and discovery of body 

On the afternoon of 24 March, police arrested a 47-year-old taxicab driver 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.

Investigation 
During a news conference on 26 March, Det Supt Fulcher stated that tests revealed that 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.

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

Trial and subsequent events 
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. The body of Becky Godden-Edwards, a woman who had been reported missing in 2007, was found after Halliwell's arrest. Halliwell had led police to the body. Mrs Justice Cox ruled that Halliwell's confessions to killing each of the women were inadmissible as evidence, as Detective Superintendent Steve 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.

On 23 April 2013, an inquest at Oxford Coroner's Court into the death of Becky Godden-Edwards recorded a narrative verdict stating that the cause of her death, believed to have been 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, Fulcher 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 Becky 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, Mr Justice Griffith-Williams sentenced Halliwell to  life imprisonment with a whole life order for the murder, meaning he will not be eligible for parole and is unlikely to ever be released from prison.

Television drama based on the case 
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 Steve Fulcher and Joe Absolom playing Christopher Halliwell.