Sussex Police are to be tried for unlawful killing for shooting dead a naked man in his own flat.

Three Court of Appeal judges headed by the Master of the Rolls, Sir Anthony Clarke, ruled that there should be a civil trial on whether police marksman, PC Chris Sherwood, was guilty of assault and battery when he shot James Ashley, of St Leonards.

Sir Anthony also said allegations of "wrongful conduct in office" by the Chief Constable of Sussex should go to trial.

Police must show that PC Sherwood, who was acquitted of murder in a criminal trial, acted in self-defence. If they cannot, a declaration of unlawful killing could be made .

Sir Anthony said the family should be permitted to take the case to court, "if only in order to seek a declaration that the deceased was unlawfully killed by PC Sherwood, especially in circumstances in which there has been no inquest or public inquiry into the death".

Edward Faulks QC, who represented Sussex Police during the hearing, told the judges: "The self defence issue is a point of great constitutional importance.

The effect of this court's order is that there will be a murder trial which could result in a declaration of unlawful killing."

His application to take the case to the House of Lords was refused. After the ruling, James Ashley's son, James, said: "Nothing will ever bring my dad back but I am very pleased with the outcome of this appeal. Maybe our family will now get some answers."

The victim's father, also called James, said: "I am happy that a court has reached a positive decision after eight years."

James Ashley was 39 when he was killed during a police raid on his flat in St Leonards in the early hours of January, 1998.

Sussex Police had a warrant to search his flat in a drugs operation. When his door was forced open, Mr Ashley went towards the door. He was shot by PC Sherwood in the neck.

His father and son are bringing civil claims against the chief constable for assault and battery, false imprisonment and negligence and - on the conduct of the police after the shooting - for misfeasance and negligence.

The chief constable has already admitted negligence in the shooting claim. The amount of compensation for the family will be set after the trial for assault and battery.

Summing up the family's allegations of misfeasance, the Court of Appeal said the officers concerned, and in particular Chief Constable Paul Whitehouse, who retired in 2001, deliberately released incorrect information to the Press and public, obstructed an independent investigation, failed to involve the Ashley family and fabricated evidence knowing that what they were doing was unlawful.

The appeal judges said the family had a real prospect of proving the allegations.

Sir Anthony said: "It is true that PC Sherwood was acquitted of murder on the direction of the trial judge. However, the burden of proof in the criminal trial was on the prosecution but in a civil trial it rests with the defendant."

He said in the criminal case the prosecution had to disprove the shooting was an honest mistake but in civil proceedings the defendant must prove the mistake was reasonable.