Five police officers are under investigation for the alleged manslaughter of a man who died after being restrained inside a hospital.
Brian Ringrose, a 24-year-old man from Milton Keynes, died on 2 February following six days in an induced coma.
He had been restrained using handcuffs and limb restraints and then carried to a police van in a “flexible lift and carry system”.
The Independent Office for Police Conduct (IOPC) said a post mortem had been conducted but that his cause of death was given as inconclusive pending further investigation.
The watchdog said Mr Ringrose was arrested by Thames Valley Police officers on the morning of 27 January.
“The officers had medical concerns for Mr Ringrose and requested an ambulance, which took him to Milton Keynes University Hospital,” a spokesperson added.
“Evidence gathered so far indicates that after being medically discharged from hospital, officers restrained Mr Ringrose in the hospital before taking him to a police van in order to transport him to police custody.
“While being taken to the van, concerns were raised regarding Mr Ringrose’s health and he was returned to the hospital where he was placed in an induced coma. Mr Ringrose sadly died in hospital on 2 February.”
Five police officers, who have not been named, are under investigation for alleged gross negligence manslaughter and unlawful act manslaughter. One of the officers is also being investigated for alleged common assault.
The officers have also been served with gross misconduct notices for potential breaches of professional behaviour related to use of force, the IOPC said.
A spokesperson added: “The decision to inform officers they are under criminal investigation means evidence indicates a criminal offence may have been committed. This does not necessarily mean criminal charges will follow.”
Thames Valley Police has suspended its use of a piece of equipment called a flexible lift and carry system which was used on Mr Ringrose as a precaution, and the IOPC is looking at its use in other forces with the National Police Chiefs’ Council.
Graham Beesley, the IOPC’s regional director for the southeast, said: “Our thoughts are with Mr Ringrose’s family and all of those affected by his tragic death. This is a significant development in our investigation and is based on evidence we have gathered to date. We have updated Mr Ringrose’s family and will now seek to interview the officers under criminal caution.
“It is our role to independently investigate all of the circumstances when someone dies in police custody.”
A spokesperson for Thames Valley Police said: “Our thoughts remain with Mr Ringrose’s family at this very difficult time.
“We have been fully cooperating with the IOPC from the outset and will continue to do so. Support is being given to the officers involved.”