A paranoid schizophrenic died after he was "unlawfully" restrained by police officers for more than 20 minutes while in custody, a court has heard.
Thomas Orchard, 32, a church caretaker, suffered a cardiac arrest in his cell at Exeter's main police station in October 2012 after being held down and a large webbing belt put across his face.
He was then freed from the restraints - making little or no movement - and left lying face down on a mattress.
Bristol Crown Court heard it was a further 12 minutes before officers re-entered Mr Orchard's locked cell and discovered he was not breathing.
He died in hospital seven days after he had been arrested on suspicion of a public order offence by Devon and Cornwall officers.
Custody Sergeant Jan Kingshott, 44, and civilian detention officers Simon Tansley, 38, and Michael Marsden, 55, are accused of the manslaughter of Mr Orchard.
Prosecutor Mark Heywood QC told the court: "He was physically restrained - both in the street, the custody unit and the van in between - for a total period of 22 minutes.
"For a significant part of the restraint time at the custody unit, he also had a webbing belt -and, to give it its full name, an emergency response belt, known as an ERB - applied over the whole or part of his face, including at times his nose and mouth.
"Once released from restraint in the cell he made little or no movement. When the cell was entered 12 minutes later, he was in cardiac arrest.
"Although cardiac function and respiratory effort were restored by advanced intervention, he died in hospital on October 10."
The three defendants face two joint charges of manslaughter. The first charge alleges that they did an act or series of acts which unlawfully killed Mr Orchard and the second alleges they unlawfully killed Mr Orchard by gross negligence.
The court heard that Mr Orchard was arrested in Sidwell Street, Exeter, on the morning of October 3and taken to Heavitree Road police station.
He was first physically restrained during his arrest and the restraint continued in the custody area of the police station and later in the cell.
"On Wednesday October 10 2012, Thomas Orchard died in hospital. By then, no medical assistance or other intervention could save his life," Mr Heywood said.
"He had been there for a week because he had sustained serious damage to his brain, the direct result of prolonged oxygen starvation on the day of his emergency admission.
"The damage that caused his death had occurred following his arrest by police on suspicion of a public order offence in central Exeter. At the roadside he was dealt with by a total of seven police officers.
"He was taken from there, in physical restraints, to the local custody unit. There he was dealt with by a total of six trained police officers and detention unit staff, again while in physical restraints throughout.
"In fact Mr Orchard was ill and he was suffering from a relapse of his mental illness, paranoid schizophrenia.
"Even so, the combination of force and physical restraints used on him on the day of his arrest, coupled, say the prosecution, with a complete failure to inquire and so to realise his true condition and also to observe him closely, led to him being starved of oxygen to the point of cardio-respiratory arrest.
"He died because force was used to restrain him, mostly in a prone - face down - position and in addition a large webbing belt was put across his face in the course of these events. Together these things interfered with his ability to breathe.
"That situation continued for rather more than five minutes while he was bound hand and foot. At the same time, say the prosecution, no-one of those directly responsible took sufficient care to see that he was breathing properly - or at all towards the end of those events.
"Instead, he was left in a locked cell, under remote observation for a further 12 minutes until his true condition was discovered. By then it was too late.
"The three defendants in your charge are those directly responsible for his detention at the police custody unit, for implementing and directing that use of force there and for the application of the webbing belt around his head at the same time.
"The prosecution say, together with a lack of monitoring, that by those actions they unlawfully caused his death. Each of them denies that what he did was unlawful and that any unlawful action of his resulted in Mr Orchard's death."