David McKittrick: The cases that would not go away without full investigation

Tony Blair appears to have approached the shooting of Pat Finucane as he did the events of Bloody Sunday: that in both cases something was badly wrong, and that neither case would go away without an inquiry.

The commitments he gave during political negotiations in the peace process four years ago are now coming into effect, with four new public inquiries on the way.

The cases are all different. The Finucane killing stands out because the accusation is that intelligence personnel were involved in the killing. The charge is that they may have let the lawyer die, or even that they manipulated their agents in the loyalist underworld to have him killed.

As the judge, Peter Cory, will point out, Army intelligence and the Special Branch in the late 1980s controlled important figures within the Ulster Defence Association (UDA), the loyalist group which has claimed more than 400 victims.

The Army version is that the military "spymasters" used this penetration to save lives and outwit the killers. The alternative version, on which the Finucane public inquiry will focus, is the allegation that the assassins were actively steered towards targets such as Pat Finucane.

This will take it into the murky area of the relationship of informers and their "handlers". Informers are unquestionably of great value to the intelligence world; the question is whether intelligence elements used them not to gather information but to have certain people killed.

In the Finucane case, Brian Nelson, a UDA member who has since died, was planted at the heart of the organisation by the Force Research Unit, a secretive Army unit.

After aninvestigation Nelson was charged and jailed, a military witness characterising him as an agent who had saved lives but gone too far.

It was said in court that Nelson had produced information which led to more than 700 reports concerning threats to more than 200 individuals. This assertion was later challenged by detectives who worked on the investigations by Sir John Stevens, the Metropolitan Police Commissioner.

The Special Branch also had its agents within the UDA, at least one of whom was involved in the Finucane killing, supplying the guns used in the murder. Information held by Special Branch was not passed to detectives after the attack. The inquiry will also consider the pattern in which Special Branch gathered information, but in many cases allegedly did not pass it on to other parts of the police force.

Judge Cory concluded that so many suspicious questions surrounded the killing, including the question of the weapons, that a public inquiry was a necessity.

In doing so he echoed the conclusion of the Metropolitan Police Commissioner, who a year ago reported that security forces had colluded in at least two murders, one of those the Finucane attack.

Sir John said he had uncovered enough evidence to lead him to believe that the Finucane killing could have been prevented, and that the police investigation into it should have resulted in the early arrest and detection of his killers.

In the case of Rosemary Nelson, another prominent defence solicitor killed by loyalists, the judge is critical of both the police and the Government. He holds them responsible for not doing enough to protect Mrs Nelson in the face of repeated loyalist threats against her.

Robert Hamill, who was kicked to death near an armoured police vehicle, is also described as a victim of police collusion because of the circumstances of his killing and the subsequent alleged wrongdoing by police officers.

The Billy Wright case is different from the others in that he was an acknowledged loyalist paramilitary leader who was killed by republicans while he was being held in the Maze prison. The judge examined the circumstances, which included an alleged laxity by the prison authorities which enabled republicans to escape from their H-block and shoot Wright as he sat in a prison van. Security cameras were said not to be functioning when the attack took place.