The police investigation into the death of showjumper Katie Simpson was flawed and failed her family, a report by the Police Ombudsman has found.
It has identified multiple failures, including a willingness to believe the account of Jonathan Creswell, the man who was later charged with her murder.
The Ombudsman also said that police were aware from an early stage of the investigation that Creswell had been convicted for assaulting another woman in 2009.
The report said there had been “a general lack of Investigative mindset” which led to her death in 2020 being treated as suicide for several months.
Disciplinary action has been taken against three officers as a result.
The ombudsman said the PSNI investigation was “hindered by the misleading working assumption that Katie’s injuries were self-inflicted”.
Multiple red flags were missed before Creswell, her sister’s partner, was eventually charged with her murder.
Ms Simpson, 21, from Tynan in County Armagh, died six days after being admitted to Altnagelvin Hospital, having never regained consciousness.
Creswell, 36, had beaten her before strangling her.
He rang 999 and pretended he had found her hanging from a stairwell.
Creswell was found dead at home while standing trial in April.
Three women charged with helping him cover up the murder received suspended sentences.
‘Not professionally curious enough’
Chief Constable Jon Boutcher has accepted there were “a number of shortcomings” in the early stages of the police investigation and has met Ms Simpson’s family to apologise.
He told a meeting of the Northern Ireland Policing Board in August that the PSNI had displayed a mindset which had not been “professionally curious enough”.
Prior to Cresswell’s arrest, several people, including relatives of Ms Simpson, had raised concerns about him.
He had a previous conviction for an attack on a woman in 2010.
The ombudsman’s investigation, which began in March 2021, resulted in a file of 1,400 pages being sent to the PSNI.
It found misconduct by a number of officers, with their cases dealt with by the PSNI’s professional standards unit.
The investigation followed a number of complaints lodged by Ms Simpson’s family and others, related to the fact that police did not treat her death as murder at an earlier stage.
They are bringing a civil action against the PSNI.
It is understood a number of further complaints related to the case have been made to the ombudsman more recently.
They are now under investigation.