Devon and Cornwall Police has pleaded guilty to health and safety breaches in relation to an emergency response belt that was used on a man before he died after being restrained in police custody.
Thomas Orchard, 32, 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.
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.
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."