Officers instigated a “cover-up” after a musician who died in custody was not treated as a medical emergency despite showing clear signs of mental illness, a misconduct hearing has been told.

Sean Rigg, a 40-year-old who had schizophrenia, died after being detained in Brixton police station in 2008 following reports he was aiming karate kicks at passers-by while semi-clothed.

Metropolitan Police constables Andrew Birks, Richard Glasson, Matthew Forward and Mark Harratt and custody Sergeant Paul White are facing misconduct charges more than a decade later, which they all deny.

Apart from Birks, they are all accused of lying about the events in order to mask their behaviour to the police watchdog, the Independent Office for Police Conduct, or the jury at Rigg’s inquest.

Gerard Boyle QC, representing the Met, said multiple witnesses reported Rigg acting as if in the grips of a mental crisis and if officers searched the police computer for the name on his passport they would have found his medical history.

Instead, Rigg was unjustifiably arrested on suspicion of stealing the passport, cuffed and held face-down in the prone position for an “excessive” period, Boyle said.

He added: “It was obvious Mr Rigg must have been suffering from mental health problems and that he should’ve been treated by the officers as a medical emergency.

“It’s simply staggering that the officers did not consider the role of mental health issues.”

They should have been aware that if there is “any doubt” of such an issue that the detainee should have been taken to A&E and not the station, he added.

Their “egregious failure” to do anything for Rigg became “more unforgivable” when they failed to help him when he was slumped on the floor in the station, Boyle added.

White, the custody sergeant, expressed a “cavalier and lackadaisical” attitude to Rigg and even falsely assumed he was under the influence of drugs or “feigning” his condition, Boyle said.

He continued: “In an attempt to cover up their behaviour, Glasson, Harratt, Forward and White have lied to investigating officers and/or a jury.”

Rigg was restrained in the prone position by three officers for more than seven minutes after being arrested in Balham, south west London, and later died after suffering a heart attack.

At the 2012 inquest into Rigg’s death, jurors found that officers had used “unsuitable” force against him.

The Crown Prosecution Service decided there was not enough evidence to bring criminal charges against any of them, other than one count of perjury against Sgt White, which he was cleared of in 2016.

The hearing continues.