Belfast, Northern Ireland (CNN) -- One of Northern Ireland's biggest terrorist trials in decades started Tuesday at Belfast Crown Court amid tight security.
Police walk into the front of Belfast Court on September 6, 2011, ahead of the trial of 14 alleged paramilitary members.
Fourteen alleged members of the pro-British or loyalist paramilitary group known as the Ulster Volunteer Force are accused of a total of 97 offenses. The men range in age from 32 to 46.
Nine defendants are charged with murder in the October 2000 slaying of rival paramilitary leader Tommy English. The 40-year-old Ulster Defence Association member was gunned down in front of his wife and young children on Halloween night during a bloody feud between the rival groups.
The Ulster Volunteer Force and Ulster Defence Association were responsible for the killings of hundreds of people during the conflict between pro-British and pro-Irish forces in Northern Ireland over a 30-year period known as the Troubles. Most of their victims were Catholic civilians. The groups have remained active since the signing of the Good Friday peace agreement in 1998.
Two brothers -- David and Robert Stewart -- are giving evidence against their alleged former colleagues in the Ulster Volunteer Force. The Stewarts admitted to their part in English's killing and agreed to testify to get a reduced sentence.
One of the accused is Mark Haddock, 42, named as a police agent in a 2007 report on the Ulster Volunteer Force by former Northern Ireland police ombudsman Nuala O'Loan. O'Loan said an Ulster Volunteer Force gang based in the Mount Vernon estate in north Belfast had been involved in up to 15 murders and that the Northern Ireland police special branch unit had allowed informers within the Mount Vernon group to act with impunity.
At trial, Haddock is sitting separately from the 13 other defendants, surrounded by prison officers for his own safety. Two of his co-defendants were previously charged with trying to kill Haddock in 2006, but murder charges were dropped when he refused to give evidence. A prosecutor opened the case Tuesday, saying Haddock had ordered English's murder.
Robert Stewart, 37, then started testifying Tuesday. He also said Haddock ordered the killing and told the gunman to try to avoid shooting the rest of English's family.
Supporters of the accused men staged a protest outside the court against the use of "supergrasses," or slang for informers. The term was first used in Northern Ireland in the 1980s when a number of terrorist suspects were convicted on the evidence of former comrades.
The trial is being held under 2005 legislation introduced by the United Kingdom -- the Serious Organized Crime and Police Act -- which allows a suspect to enter a written agreement to give evidence against other alleged criminals.
Victims' relatives are being given protection from supporters of the Ulster Volunteer Force attending the trial at Laganside courts in Belfast. Families are able to watch proceedings by video link in a separate, secure venue. Large numbers of police officers are inside and outside the court complex.
The trial could last three months and will be one of the most expensive ever in Northern Ireland. Police fear there could be unrest in Protestant/loyalist districts as the trial progresses.