Mr Justice Barr said the second leg of the prosecution case was the evidence of Charles Bowden.
The judge called the witness "an admitted accomplice in the murder of Ms Guerin, who also implicates the accused as one of those who participated in the planning of the murder and who, he alleges, in accordance with that plan, provided a crucial back-up service for the actual killers by taking charge of the motorcycle and the gun used in the crime at his home soon after the event and subsequently disposing of both."
The judge went on: "What may have been the motorcycle in question was later found broken up in the River Liffey, but the gun was never found and no information emerged at the trial as to what became of it. There is no doubt that at all times the Garda has been most anxious to trace the weapon."
The judge said the court was satisfied Bowden is not a "supergrass" in the sense relating to Northern Ireland, but when admitting his own part in the Guerin murder and in implicating others, he furnished information to the police "as a cornered criminal to extricate himself in part at least from a grievous situation in which he found himself."
"The court accepts without any doubt that Charles Bowden is a self-serving, deeply avaricious and potentially vicious criminal. On his own admission he is a liar and the court readily accepts that he would lie without hesitation and regardless of the consequences for others if he perceived it to be in his own interest to do so."
The judge said the reason given by Bowden for his sudden decision to tell the truth "borders on the absurd and is totally rejected by the court."
"The court is satisfied that Mr Bowden is not the sort of man to have been overcome with grief or remorse about the killing of Ms Guerin. On the contrary, like other senior members of the gang, he had good reason to welcome her death, whoever her assassins may have been, bearing in mind that his leader [a named man], the linchpin in a major criminal business enterprise, faced a probable jail term on Ms Guerin's account which was likely to cripple the business for the period of his enforced absence to the great detriment of all, including his lieutenant, Bowden."
The court accepted the evidence of Mr Senan Molony, a journalist and former neighbour of Bowden, that there was a "raucous party" at the Bowden house on the night of the Guerin murder.
"Mr Bowden is an intelligent man. The court is satisfied that the reason for his conversion to the alleged truth had nothing to do with remorse, as he contends, but is the product of a cold dispassionate assessment of his grievous situation at that time and amounted to a decision on his part to extricate himself as best he could from what he probably perceived to be the reality of his situation then.
"The court is satisfied that Bowden was motivated by self-interest in voluntarily admitting his own involvement and that of others in the murder of Ms Guerin.
"He has agreed to turn State evidence in this and other related trials in return for a written undertaking from the Director of Public Prosecutions not to prosecute him for the murder of Ms Guerin. He has also obtained modest prison sentences, having pleaded guilty to major drugs and arms crimes. He has secured special concessions while in prison and his wife and children have been given the benefit of the witness protection programme.
"Although not yet finally negotiated, it seems likely that when Bowden serves his sentence or earlier he will be released and set up with a new identity in a foreign country and some money in lieu of his substantial ill-gotten gains will be provided for him."
The judge said there was no doubt that it would be in Bowden's best interest to tell the truth about all the details relating to the Guerin murder. Bowden's evidence had been corroborated in its essentials by the accused.
The judge said there did not appear to be anything to suggest falsely implicating Ward in the crime might have been of advantage to Bowden.
Giving the background to the crime as outlined by Bowden, the judge said that a named man was the leader and linchpin of a huge cannabis importing and distribution business in Ireland which also appears to have extended outside the State.
The gang leader had five "senior line managers", including Bowden and the accused, who were responsible for receiving large consignments of drugs which were taken to a premises in Dublin from where they were delivered to customers. The court said the five "lieutenants" had net earnings in the region of £150,000 pounds a year and probably substantially more.
There was no evidence as to what the profit for the leader was but it was reasonable to conclude that it was "very substantial."
The court said Ms Guerin had an encounter with the gang leader in January 1996 and he had been charged with assault.
"This enraged him because on imprisonment on foot of a likely jail sentence grave harm would be done to his cannabis empire because he would be prevented from purchasing supplies and arranging for the importation of the product into Ireland. It is also probable that he perceived himself as being hugely important in the criminal world and it would be a source of great annoyance and humiliation to be sent to jail as a petty criminal.
"The end result was that a plot was hatched to murder Ms Guerin and thus the prosecution which she had initiated against [the named leader] would have to be dropped as it was dependent on her evidence."
The judge said that according to Bowden there were two performers in the murder, the man who rode the motorbike and "a hired killer" who shot Ms Guerin six times. "Is it likely that Bowden has given a truthful account of [the rider's] involvement in the murder? The court is satisfied that his evidence in that regard has a strong ring of truth about it." The judge said that it was "entirely credible" a professional killer would have been hired for the killing. "All in all, Bowden's evidence about the accused's involvement in the crime also has a strong ring of truth about it."
"We come then to the question, which is at the root of this case, is there any basis on which the court might reasonably suspect that Bowden had an interest to lie about the accused and wrongly implicate him in the crime of murdering Ms Guerin? As already stated, if in assessment of the evidence the court has a reasonable doubt that that might be so, then Bowden's evidence against the accused must be rejected. The court can find nothing in the evidence which raises such a suspicion."