Public money will be used to fund a fight by police officers to overturn an inquest verdict of unlawful killing.
Roger Sylvester fell into a coma after he stopped breathing
Eight officers were suspended after last October's ruling that unreasonable force was used to restrain Roger Sylvester.
Mr Sylvester, 30, from Tottenham, north London, died in 1999.
The Metropolitan Police Authority's decision to pay the costs has been criticised by supporters of the Sylvester family, and Ken Livingstone.
The Metropolitan Police officers want a judicial review of the jury verdict, insisting Mr Sylvester was restrained in line with police guidelines.
The council worker collapsed after being restrained in a padded room at a psychiatric hospital.
'Waste of money'
He was in a coma for seven days before he was pronounced dead on 18 January.
The inquest jury ruled he died from brain damage and cardiac arrest due to breathing difficulties caused by restraint.
London Mayor Ken Livingstone called the appeal decision a "waste of public money".
Glen Smyth, chairman of the Metropolitan Police Federation, said: "Ken Livingstone should stay out of this because these are matters for the police authority and not the mayor.
"He does not have political control of the police."
Some of Mr Sylvester's family were refused legal aid
Mr Livingstone had added his voice to the growing condemnation of the decision from the Sylvester family and some civil rights campaigners.
They point out that when the judicial review begins, Mr Sylvester's elderly relatives will be forced to pay their own bills because they have been refused legal aid.
Mr Livingstone said: "The decision by the MPA committee to fund this appeal is a waste of public funds.
"This is an extremely sensitive case and I would urge the full Metropolitan Police Authority to look into this decision as a matter or urgency."
A date for the judicial review has yet to be set.