Six police officers were cleared yesterday over the death in custody of a man run down by a squad car.

Michael Powell, 38, who had been suffering from mental health problems, was detained after a late-night disturbance at his mother's home in Birmingham in September 2003.

After the car drove into him, he was sprayed with CS gas and struck with a baton. He was then restrained on the ground until a police van arrived.

He was taken to Thornhill Road police station and an ambulance was called. He died a short while later.

A total of 10 officers were accused of either attacking the father-of-three or failing to call medical help.

The prosecution produced CCTV footage from the police station, the soundtrack of which seemed to contain evidence of the officers' desperate attempts to revive Mr Powell, a cousin of the poet Benjamin Zephaniah.

Jurors at Leicester Crown Court had listened to snatches of conversation in which the men, according to the transcript, said: "We're in the shit," "gone unconscious" and "Michael, come on."

But the evidence was ruled unsafe because the television set in the room was playing a Frederick Forsyth film, The Dogs of War, and it was impossible to tell which voices were which.

Under cross-examination, Prof John French, a sound expert, admitted that "gone unconscious" was actually "formal protest" from the 1981 film, which concerns an attempted African coup by a group of mercenaries.

A police officer's "How are you doing?" was actually an actor saying "Can you hear me?".

Judge Sir Douglas Brown therefore directed the jury to clear four officers of misconduct in public office in June, midway through the trial. They were Pcs Lee Howard, Andrew Edwards and Luke Gill and Custody Sgt David Williams.

He noted: "It is one of the extraordinary features of this case that nobody in the early stages of this investigation had thought that it might be worth inquiring what the film was. It was left to the defence to buy a copy of the film."

Yesterday the jury found the remaining six officers not guilty.

Insp Anthony Guest, Acting Sgt Chris Wilson, and Pcs Nigel Hackett and Steven Hollyman were cleared of misconduct, and Pcs Tim Lewis and David Hadley of battery, although the jury failed to reach a verdict on whether these two were guilty of dangerous driving.

Jan Berry, the chairman of the Police Federation, called for "an urgent review" of the case, which she said should never have gone to court.

"By pursuing this prosecution, the Crown Prosecution Service and the Independent Police Complaints Commission have failed the victim and his family, the police officers and the criminal justice system," she said.

In response, John Crawley, a police complaints commissioner, defended what he called "a thorough, robust and professional investigation which can only bring credit to the police service."

But Mr Powell's family and friends described the outcome as "a travesty of justice."

They said in a statement: "This is yet another instance where a fit young man has come into contact with the police ? and within a matter of hours is pronounced dead."