In 2001 a retired Canadian judge, Peter Cory, was appointed by the British and Irish governments to examine allegations of collusion on both sides of the border by some members of the security forces in some of the most controversial killings of the Troubles. He recommended a public inquiry into five of the following six cases.
The inquiry into the murder of the founder and leader of the Loyalist Volunteer Force (LVF) started in May - 10 years after his death and four years after it was recommended by Judge Cory.
It is taking place in a refurbished court house in Banbridge, a country town south of Belfast.
The inquiry has been tasked with deciding if the British government colluded with Wright's killers, who were members of the Irish National Liberation Army (INLA).
Wright, dubbed King Rat by some journalists, founded the LVF in 1996.
He is suspected of involvement in the murders of several Catholics in the Portadown and Lurgan area between the mid 1980s and his death in December 1997.
Wright is believed to have sanctioned up to 20 murders during his reign.
He was sent back to jail in March 1997 and was assassinated by three INLA inmates in the Maze prison on 27 December 1997. They were later convicted of murder but released under the Good Friday Agreement.
It has been alleged that MI5, the Royal Ulster Constabulary (the forerunner of the Police Service of Northern Ireland) and the Northern Ireland Prison Service turned a blind eye to the INLA's plan to get rid of Wright.
Although his death destabilised the already fragile peace process, the Good Friday Agreement was signed four months later, heralding the end of the Troubles.
There has also been speculation that Wright was a British government agent.
The February 1989 killing of high-profile solicitor Pat Finucane by Ulster Defence Association (UDA) paramilitaries remains one of the most controversial of more than 30 years of conflict.
He was shot 14 times as he was eating a Sunday meal at home. The attack, which wounded his wife, was witnessed by the couple's three children.
Mr Finucane was deemed a target because he was a defence lawyer who had represented a number of alleged IRA members in court.
Brian Nelson, a double-agent within the UDA, had been asked to compile a dossier on Mr Finucane, a fact he claimed was known by his handlers in the security forces.
Judge Cory recommended a full and public inquiry but it is yet to be established.
Delays have been caused by the trial of loyalist Ken Barrett, who was jailed for life in 2004 for Mr Finucane's murder, and legal wranglings over how the inquiry should be conducted.
The Finucane family say it will not be able to establish the truth as it is being held under the Inquiries Act, which means a British government minister can rule whether the inquiry sits in public or private.
Rosemary Nelson, like Mr Finucane, was a prominent lawyer in Northern Ireland.
She had made her name as a human rights lawyer representing nationalist residents of Portadown, who were embroiled in a dispute over the Drumcree Orange Order parade.
The Catholic mother-of-three was killed by a booby-trap car bomb near her home in Lurgan, County Armagh, in 1999.
Loyalist paramilitary splinter group, the Red Hand Defenders, claimed responsibility for her murder.
There have been allegations of security force collusion in the killing of Mrs Nelson, who claimed she had received death threats from members of the police.
Her death came two weeks before she had been expected to meet a police watchdog about the threats.
The inquiry into the murder of Mrs Nelson opened in April 2005.
The three-member panel has been appointed and the full hearing was due to start in January but it has been delayed until September 2007.
More than 300 people have provided witness statements and 140 people have been interviewed in Northern Ireland and elsewhere.
Robert Hamill, a 25-year-old Catholic father of two, was killed by loyalists in Portadown in 1997.
Unable to hail a taxi after a night out, he and his friends decided to walk home.
They thought it would be safe to walk through the city centre as RUC officers were on patrol.
Mr Hamill was set upon and beaten to death. He was rushed to hospital but died 12 days later.
No-one has been convicted over his death.
Police have denied eyewitness claims that four RUC officers in a Land Rover saw what was happening and failed to intervene.
The inquiry into Mr Hamill's death has been set up to determine if there was any wrongful act or omission by police which facilitated Mr Hamill's death or obstruction of the investigation into it.
The inquiry panel was set up in December 2004.
It has been hampered by legal issues, particularly surrounding the anonymity of witnesses, and no date has been set for the full hearing.
Ex-RUC officers won the right to anonymity when they come to testify but this decision is being appealed.
HARRY BREEN AND BOB BUCHANAN
Chief Superintendent Harry Breen was shot dead near Jonesborough in south Armagh in 1989, along with his colleague Superintendent Bob Buchanan.
Chief Supt Breen was the highest-ranking RUC officer to be killed by the IRA.
The policemen were ambushed on the border after returning in an unmarked car from a meeting with in Dundalk with their counterparts in the Garda Siochana.
Two senior RUC officers were shot after visit to Irish Republic
Supt Buchanan, a father-of-two, died at the wheel as he attempted to put the car in reverse. Chief Supt Breen, who also had two children, was found dead at the roadside.
The IRA took security documents from the car.
There have been suspicions that a rogue Garda officer in the Republic may have tipped off the IRA about their movements.
In his report Judge Cory said while the IRA did not need information from Irish police to murder the officers, two separate intelligence reports referred to a Garda leak.
The inquiry into the allegations opened in Dublin in March 2006.
LORD AND LADY GIBSON
Lord Justice Maurice Gibson was the second most important figure in the Belfast judiciary when he was killed.
Despite the tight police protection awarded to all judges, the IRA managed to find a chink in his armour.
Lord Justice and his wife Lady Cecily were killed by an remote-controlled car bomb as they drove over the Irish border back into Northern Ireland after a holiday in April 1987.
As the judge's car reached the border, he stopped to shake hands with the Garda security escort who had completed their part of the security assignment. The couple had only a short drive to meet the RUC escort to Belfast.
The bomb lay between the two points. The explosion threw the Gibson's vehicle across the road, killing the couple immediately.
An investigation into the murders concluded the IRA had somehow discovered the couple's holiday plans. Some unionists blamed an IRA mole within the Garda.
Judge Cory said he found no evidence of collusion in the Gibson case and did not recommend an inquiry.