BBC Ireland correspondent Kevin Connolly gives his analysis of what the Stevens Inquiry means.
What is this report about?
We think it will say that there was collusion between people in the RUC Special Branch, the British Army, and loyalist paramilitaries.
In effect a certain element within the security forces was using the UDA almost as a wing of their own operations.
So for example when Pat Finucane was killed in 1989 there was a sinister and faintly ludicrous situation where most of the loyalist gang that killed him were either agents or informants for various different British security agencies.
And yet somehow the killing went ahead and this I think will be the focus of Sir John Steven's third enquiry.
We have to remember that he has been looking at this whole issue of collusion for an incredible amount of time: It's taken 13 years to produce three separate reports.
Embarrassing for the authorities and of course it raises issues about practices for the authorities in the future.
Will this report lead to prosecutions?
It might. We are quite a long way from that yet.
What's happening is that Sir John forwarded papers on 20 cases to the director of public prosecutions and that's where the decision-making will be made.
So there may be court cases arising from this and they are in some cases quite sensitive.
We are told they certainly include former and serving members of the security forces.
Are we talking about a few people who were involved - or something more widespread and officially sanctioned?
Sanctioned from above is something we don't know.
Certainly in political terms we know Sir John has spoken to at least one former Northern Ireland Secretary.
But there's no evidence whether there was political direction of this.
The whole question is whether this was just a few mavericks or whether it was systematic.
I think the impression from Sir John's report is that it was so widespread and it was done on such an extensive scale that it was a really important part of how at least one element of the security forces were operating at the height of the Troubles.
They were collaborating with loyalist killers who were murdering innocent Catholics - and the targeting process was being done jointly by intelligence officers and by terrorists.