Lawyers for eight Met officers aiming to overturn an unlawful killing inquest verdict have told the High Court the ruling was "irrational and perverse".
Roger Sylvester fell into a coma after he stopped breathing
They are seeking a judicial review of last October's ruling into the death of Roger Sylvester in Tottenham, north London, in January 1999.
The jury ruled he died from brain damage and cardiac arrest after being restrained by the policemen.
The officers' lawyers said there was not enough evidence to support this.
On Wednesday, Michael Bromley-Martin, QC, told the High Court that the inquest was irrational but "not because the jurors were mad or irrational, but that something must have gone wrong in the inquisitorial process to allow that to happen."
He added: "It is clear that somehow the essential issue in the case became lost by the time the jury completed the inquisition."
He also said that the coroner at St Pancras, Dr Andrew Reid, should never have left the unlawful killing verdict to the jury.
Mr Sylvester, 30, had suffered from mental health and drug problems, and was detained naked and banging on his own front door.
He collapsed, after being restrained in a padded room at a psychiatric hospital, and was in a coma for seven days before being pronounced dead on 18 January 1999.
In reaching its verdict, the jury concluded Mr Sylvester had been restrained for too long, in the wrong position, and was not given sufficient medical attention.
The officers involved insist council worker Mr Sylvester was restrained in line with police guidelines.
And pathologists at the inquest were unable to agree on the cause of death.
Mr Bromley-Martin said the entire basis of dispute was whether Mr Sylvester had been held with "more force than necessary and for longer than necessary".
But he added "particular care and concern" should have been taken during the inquest because of its importance not just to the Sylvester family and the police, but also because of "the public implications behind any verdict of the jury".
The Sylvester family are expected to argue during the three-day hearing that the verdict was justified.
Bernard Renwick, Roger Sylvester's brother, said before Wednesday's hearing: "Where would be the justice if an unlawful killing verdict beyond reasonable doubt, reached by a jury of eleven, is replaced with accidental death, or an open verdict by a single judge?"
The ruling is expected in about four weeks.