The use of supergrasses in Northern Ireland as a means of convicting terrorists has been littered with failures. It was a tactic used frequently during the early Eighties when 25 men turned Queen's Evidence over a period of three years to put hundreds of loyalist and republican paramilitaries behind bars. But the system collapsed in 1985 and most of those either jailed or on remand were released. Two recent cases relying on the evidence of self-confessed loyalist terrorists have also failed spectacularly.
In both cases – the Stewart brothers who gave evidence against 13 alleged UDA members in north Belfast and Neil Hyde, a suspect in the murder of journalist Martin O'Hagan – the supergrasses were deemed to have lied, or withheld the whole truth about terrorist acts they were involved in. That goes to the nub of the problem with reliance on the evidence of known terrorists. By the very nature of their associations they will have been involved in very unsavoury criminal activity.
The use of supergrasses shows that police and prosecutors find it difficult to convict terrorists by conventional detective work. Both loyalists and republicans are adept at covering their tracks and also carry sufficient menace even now to discourage members of the public giving evidence against them. It is little wonder that the authorities turn to those who profess inside knowledge of crimes to help them put the guilty behind bars.
But as the failures show, supergrass evidence has to pass many tests. The informer's character inevitably will be disputed and the system of giving reduced sentences in return for evidence will also lead to claims that this is an incentive to lie or embellish the truth. However, the use of informers can be useful if carefully controlled and if some collaborative evidence can be established.
The tactic should not be dismissed out of hand, but the police and prosecution must ensure that cases are as watertight as possible before going to trial as any more expensive failures will undermine public confidence in this method of tackling terrorism.