Devon and Cornwall Police has pleaded guilty to health and safety breaches after using an emergency response belt on a man before he died in custody.
Thomas Orchard, died in hospital seven days after being arrested and taken to Heavitree Road police station in Exeter, Devon, in October 2012.
During his detention Mr Orchard, who had paranoid schizophrenia, was restrained and an Emergency Response Belt (ERB) was placed across his face.
He was then left in a locked cell, where he lay apparently motionless for 12 minutes before custody staff re-entered and commenced CPR.
The chief constable of Devon and Cornwall Police Shaun Sawyer has said he can now express his “deepest regret” to the family of Thomas Orchard.
In a statement, he said: “In the intervening six years, my thoughts have always been with Thomas, his family and friends who have lost a loved one.
“It is only today that I have been able to personally offer my deepest regret to all those individuals.
“In the spirit of candour and out of respect to the courts, the family of Thomas, the public and my workforce, I have decided – as the corporate responsibility of this organisation, that it is only right to plead guilty on behalf of Devon and Cornwall Police to this charge.
“However, legal matters remain outstanding in respect of whether this health and safety breach caused the death of Thomas.
“We must respect this court process as the judge is still to make a determination on this very issue, and it is not for Devon and Cornwall Police to make a decision on such a critical matter."
In March 2017, a custody sergeant and two staff members from Devon and Cornwall Police were acquitted of Mr Orchard's manslaughter by gross negligence.
A year later, the Crown Prosecution Service announced it had charged the office of the chief constable of the force under the Health and Safety at Work Act 1974.
Shaun Sawyer, the chief constable, appeared at Bristol Crown Court on behalf of the force and entered a guilty plea to the single charge against it.
The court heard the issue of whether the breaches causes Mr Orchard's death has not been resolved between prosecution and defence teams.
Judge Julian Lambert will decide on the issue during a hearing, expected to last for three days, in April next year.
Prosecuting, Mark Heywood QC, told the judge: “Both parties are agreed that this is a multi-factorial case.
“The issue is whether or not restriction of breathing by application of the belt was a contributory factor [of death].”
The hearing in April will include evidence of Mr Orchard's restraint, including CCTV footage and witnesses.
The judge will also consider the degree of training in relation to the ERB, "which is at the heart of the case", Mr Heywood said.
Jason Beer QC, representing the office of the chief constable for Devon and Cornwall Police, told the court: "The principal issue between the parties is causation and there is a subsidiary issue of training."