Loyalist killer Michael Stone could walk free from prison in eight years after he escaped a life sentence yesterday for trying to kill senior Sinn Fein leaders.

The 53-year-old was jailed for 16 years at Belfast Crown Court for the attempted murders of Gerry Adams and Martin McGuinness in a bizarre armed attack on the Northern Ireland Assembly.

However, the former UDA member, who gained notoriety in 1988 when he killed three mourners at an IRA funeral in west Belfast, will be eligible to have that sentence halved.

The father of nine, who claimed his actions at Stormont in November 2006 were performance art, was convicted of six murders in 1989, but granted early release on license in 2000 under the terms of the Good Friday Agreement.

His license was suspended in the wake of the incident at Parliament Buildings and the Sentence Review Commissioners will now decide whether or not his license should be revoked. If as expected they do, the authorities would set a minimum term he should spend in prison for the 1989 convictions.

However, the Prison Service said both time already served in prison and time spent out on release on license (a total of more than 20 years) will form part of the tariff.

Therefore, if the tariff is set at 28 years or less, Stone could be considered for release once he has served half of the 16-year sentence for the Stormont attack.

The decision to set him free will then rest with Parole Commissioners. The highest minimum tariff ever set in Northern Ireland is 35 years.

Handing down his sentence yesterday, Mr Justice Deeney told Stone he had decided not to give him a life term on the grounds that his actions had not resulted in any serious injury and the fact he suffers from a degenerative muscle-wasting condition. He acknowledged this disease would see him confined to a wheelchair in the future. However, the judge said he also had to consider the serious nature of the offences that Stone had already committed before the events at Stormont.

“He could hardly have a worse criminal record,” said Mr Deeney, “and I do take into account the very grave offences of which he was convicted in 1989.”

Stone, dressed in denim, sat impassively as the sentence was delivered. During his four-and-a-half week non-jury trial, his defence team had claimed his actions at Parliament Buildings were part of an elaborate comic parody.

However, delivering his verdict last month Mr Deeney dismissed this theory as unbelievable.

As well as two attempted murder counts, Stone was found guilty of seven other charges relating to the Stormont attack, including possession of nail bombs, three knives, a garrotte, an axe, and causing criminal damage to the Stormont building.