PC Christopher Sherwood, the officer who fired the fatal bullet, was rated a good shot.

He had passed a rigorous test in weapons and tactics before applying to become an authorised firearms officer at Gatwick Airport.

With two years' probation at Hailsham, since joining Sussex Police at the age of 23, already under his belt, PC Sherwood passed training to become a member of the force's Special Operations Unit just over a year before the raid.

The training included target recognition and the ability to distinguish a threat.

So when he saw Mr Ashley coming at him in the darkness he acted instinctively - and shot him dead.

PC Sherwood was suspended from duty and in March 1999, he was charged with murder. Almost two years later his trial began at the Old Bailey in London.

He denied the charge and judge Mrs Justice Rafferty halted the trial at the end of the prosecution case directing the jury to find him not guilty.

She agreed with the defence which argued the Crown had been unable to explain how PC Sherwood was a reputable police officer doing his duty outside Mr Ashley's bedroom door but within seconds had turned into a murderer once inside the bedroom.

The court heard the raid on the block of flats in St Leonards should never have been authorised. Reports of the threat posed by Mr Ashley had been overstated and the tactics used should only have been employed as a last resort.

The 25 armed officers were told a gun was in the flat along with a kilo of cocaine and an associate of Mr Ashley's who was wanted for a stabbing.

Yet when the police burst in, Mr Ashley was unarmed and naked in bed with his teenage girlfriend.

The man wanted for the stabbing was not in the building and instead of a drugs haul all that was found was a tiny amount of cannabis which Ashley had for personal use.

Insufficient planning meant the group in three teams of five officers had no internal plan of the building and the element of surprise was lost when a dog started barking.

The noise woke up Mr Ashley's girlfriend, Caroline Courtland-Smith, and forced Mr Ashley out of bed just as PC Sherwood burst in.

In that split second PC Sherwood recognised the man from one of the photographs shown at the pre-operation briefing.

The officer said: "I thought he was going to shoot me, kill me, so I reacted by firing my gun."

Mr Ashley slumped to the ground and the shocked officer tried to stem the flow of blood as he called for a medic.

A tape played to the jury showed just 34 seconds had elapsed between the order to strike and the call for a medic. The time between PC Sherwood entering the bedroom and pulling the trigger was estimated at three seconds.

Opening the prosecution case on PC Sherwood's 34th birthday, Nigel Sweeney admitted the armed entry should never have taken place and both the planning and briefing of the team was "defective".

He said: "Taking part in a police operation is not a licence to shoot. It is not an immunity from prosecution. If a shot is to be fired it must be lawfully fired."

He held up the 2ft-long Hechler and Koch carbine gun fitted with a red-dot sight and torch which PC Sherwood fired at Mr Ashley when he went into his flat dressed in a uniform known as 'blacks' which included body armour and goggles.

The officer said Mr Ashley had come towards him raising his hands saying: "What the f*** are you doing?"

Mr Sweeney said: "He claimed that he thought a gun was being levelled at him ready to fire and he had reacted instinctively in fear of his life and thus his decision to pull the trigger."

Later PC Sherwood said he had not seen hands but saw Mr Ashley's arms coming close together and he thought his own life was at risk.

He told other officers: "I shot him. I just shot him. He came straight at me."

The court was told PC Sherwood had a sight problem when he was tested after the shooting but it did not "make him prone to seeing things that were not there".

The jury heard the operation was doomed from the start when senior officers seeking authority for the raid from Deputy Chief Constable Mark Jordan outlined a picture which was "simply not true".

Other officers giving evidence said due to the briefing they were conscious of a "high degree of risk and danger".

Just after 4am the Special Operations Unit moved into position using Saxon Street, close to the flats in Edinburgh Mews, as their forming-up point.

Police managed to obtain a duplicate key to the communal front door of the building and two officers armed with revolvers were the first inside to find the location of the three flats to be raided.

They then led the three assault teams up the stairs into position to wait for the order to strike.

PC Jerry Kilshaw told defence counsel Nicholas Purnell QC that he had mentally gone through his training routine two or three times as the tension mounted.

Sgt Donald Moyse, who was leader of Team 5, which included PC Sherwood, said it had come over particularly strongly during the briefing that Mr Ashley had no fear of violence and had been involved in a drugs operation where intimidation, threats, a shotgun and knives were mentioned.

He said: "What I went away with is the impression we were dealing with somebody who was a great personal threat to anyone encroaching on his territory."

He said there was a knot in his stomach and he was slightly shaking through anticipation of action as he waited on the stairs for the order to strike.

PC Simon Hunt, who was the door enforcer for the team, said he thought there was a gun in the flat and that a person associated with the address had been involved in a shooting incident.

He told the jury that he did not need to force open the door of Ashley's flat because it was unlocked and he only had to turn the handle before flattening himself against the wall to let the officers get past.

PC Hunt said the way officers were sent in allowed them to "flow like water" through a property and prevented officers from pre-judging what was inside.

However, firearms expert Superintendent Alan Bailey, of West Mercia Police, told the court he found the statement "illogical".

He told the jury: "In any dangerous situation the more knowledge you have the safer and more professional you can be in the way you deal with it."

Mr Bailey, one of the country's leading experts on police firearms operations, told the jury that the decision to authorise the raid had put both PC Sherwood and James Ashley in unnecessary danger.

Questioned by Sherwood's defence counsel Nicholas Purnell QC, he said that he would have advised against attempting the operation.

He said: "It was the last and least appropriate drill to use in these circumstances."

He said that successful police firearms operations were totally dependent on teamwork and regular training as a collective unit and he would never have allowed the officers taking part in the Sussex raid to have been formed into teams in which some were trained in armed intervention tactics and others were not.

Mr Purnell said: "Every failure allowed James Ashley to be woken, get out of bed and move towards the door making confrontation, if not inevitable, highly likely.

"As a senior police officer you would not have allowed PC Sherwood to be put in that position?"

Mr Bailey said: "Yes, sir."

Sgt William Bradley, a member of the West Mercia Constabulary and an instructor at the national firearms training school, gave evidence that the 'Bermuda' tactic used by the officers for fast room domination should only be used as a last resort.

Caroline Courtland-Smith, now 22, described how she was woken by the sound of banging and thought a burglary was taking place.

She woke Mr Ashley who, half asleep, first went towards the window and started walking round the end of the bed when the door opened and PC Sherwood and two other officers walked in and shot him.

At first she thought he had been stunned by a rubber bullet as he disappeared from view.

Another officer held her down on the bed and told her not to move.

She said: "Reality was slowly setting in. More and more people started filing into the room. It seemed like panic was going on. It didn't seem organised at all."

Miss Courtland-Smith said one of the officers shouted "get her out of here" and she was pushed out of the room with the duvet wrapped around her.

She said she then saw Mr Ashley had been put in the recovery position and there was a blood stain on the wall.

"Then it sunk in they had shot him with a real gun. There was just blood everywhere."

Mr Sweeney told the jury during a four-hour opening speech that it was a case where one could feel sympathy for both sides.

He said: "There is sympathy for the dead man, shot for no good reason, sympathy for the girlfriend who witnessed it and for the family who lost him.

"Equally, it is possible to feel sympathy for the defendant, sent on an operation which the Crown concede should not have taken place and in which there were various defects."

He warned the jury the case was not about sympathy and needed a cool, careful and calm assessment of the evidence.

But the jury was never asked to decide if PC Sherwood was guilty of murder or manslaughter after being directed to find the officer not guilty on both counts at the end of the prosecution case.