A mixture of restraint and struggle in severe agitation caused the death of a man who died after he was held down by 11 police officers at a psychiatric hospital, a jury has been told.

Olaseni Lewis lost consciousness after being pinned down when he became agitated in the care of staff at Bethlem Royal Hospital in Beckenham on August 31, 2010.

Dr Ashley Fegan-Earl, the forensic pathologist who examined the IT graduate’s body, today told his inquest that a “vicious cycle” caused him to collapse into cardiac arrest.

RELATED: Inquest of graduate Olaseni Lewis who died after being restrained by 11 police officers at a Bethlem Hospital in Beckenham opened

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Olaseni Lewis, also known as Seni, pictured with his mother Abijola

He said that in a state of acute behavioural disturbance (ABD), Mr Lewis’ struggle and muscle demands while being restrained by officers affected his pulse rate and breathing and, in part, caused his heart to stop.

A “significant” lack of oxygen to the 23-year-old’s brain as a result of the cardiac arrest then caused the death of the South Norwood graduate, according to Dr Fegan-Earl.

He told the senior Coroner for south London Selena Lynch: “A mixture of forces could have caused the heart to stop.”

When asked by the Coroner whether Mr Lewis’s ABD could be the sole cause of his death, he said “it is a difficult question to answer.”

He added: “The problem becomes that the individual who is in distress may become exposed to the police because of that distress.

“The processes become inextricably linked… A vicious cycle of things, one thing leading to another.”

ABD is defined as a triad of acute delirium, severe agitation or aggression and disturbance to the nervous system.

Dr Fegan-Earl examined Mr Lewis’s body for injuries potentially sustained in the events that led to his death.

Though he found several minor injuries to his thighs and shoulders, the forensic pathologist said nothing he found caused Mr Lewis’s death.

On external injuries Mr Lewis, received, Dr Fegan-Earl added: “There was no evidence of any injuries to his neck that would suggest he was gripped [while being restrained].”

On internal injuries, he said bruising to the chest bone was found but no there were no fractures of the ribs.

Coroner Lynch asked if the bruising was the result of being knelt on by police officers while they restrained him.

Dr Fegan-Earl said: “It’s not unusual to see bruising in that area [after use of a defibrillator]… There’s no way of defining which caused the injury.”

His conclusions, given to a jury of five men and six women at south London Coroners’ Court, were that Mr Lewis died of a hypoxic brain injury caused by restraint and acute behaviour disturbance.

The first of two defibrillators used to try and resuscitate Mr Lewis could have not been working, the jury were told by professor of resuscitation Jerry Nolan.

Giving evidence in court this afternoon, he said: “[The defibrillator is] battery powered and if taken out of the machine for more than two hours, the clock needs to be reset.

“It is entirely possible that the battery had gone down and or had been changed and the time not reset.”

The inquest, which is being held in Croydon’s Davis House and is expected to last a total of 10 weeks, continues.