RTÉ's Richard Dowling examines one of the critical issues faced by Judge Peter Smithwick

How do you define collusion?

That's the first issue that has to be decided upon before any ruling can be made as to whether collusion actually took place. It may sound simple and straightforward - but it isn't.

There have been several definitions of collusion in several probes into several murders during the Troubles.

The version adopted by Judge Peter Smithwick is quite wide in its scope, allowing findings of collusion where other investigations would have found no collusion although the facts would be the same.

He decided that collusion could be established if there was action - or inaction - by an individual or police.

Everyone accepts the basic minimum of collusion - that someone working for the State, or a State body itself actively participated in the killing of a person. But it's in areas like "turning a blind eye" or omissions that there is divergence.

The first working definition was drawn up by Sir John Stevens who was investigating claims of State collusion with loyalists in several murders.

In his view collusion..."is evidenced in many ways. This ranges from the wilful failure to keep records, the absence of accountability, the withholding of intelligence and evidence, through to the extreme of agents being involved in murder."

Retired Canadian Judge, Peter Cory, who also investigated several controversial killings said collision should be defined "reasonably broadly" to ensure public confidence in the body being probed: "Because of the necessity for public confidence in the army and police, the definition of collusion must be reasonably broad when it is applied to actions of these agencies.

"This is to say that army and police forces must not act collusively by ignoring or turning a blind eye to the wrongful acts of their servants or agents or supplying information to assist them in their wrongful acts or encouraging them to commit wrongful acts.

"Any lesser definition would have the effect of condoning, or even encouraging, state involvement in crimes, thereby shattering all public confidence in these important agencies."

The same definition was used by the first Northern Ireland Police Ombudsman, Nuala O'Loan, when she investigated allegations of collusion.

She found there was State collusion in the murder of Raymond McCord Jnr for example.

However, her successor Al Hutchinson, a former Canadian policeman, adopted a very different view of what constitutes collusion.

In his February, 2011 report into the bomb attack on McGurk's Bar in Belfast, he said the term collusion was ill-defined and decided that there was no evidence of State collusion in the attack which killed 15 people.

His view of collusion is that it...."requires that a number of elements be present. Usually, but not always, it involves an agreement between two or more parties.

"There is an additional requirement that a sufficiency of evidence exists to establish, on balance, that the act or omission complained of was deliberate and not merely negligent or inadvertent."

The last part of that definition is particularly worthy of note.

The key word is "deliberate".

This definition is significantly different from the definition used by Judge Smithwick in the Smithwick Tribunal.

In his opening address in 2006 he gave his view of what would constitute collusion in his investigation.

"The issue of collusion will be examined in the broadest sense of the word. While it generally means the commission of an act, I am of the view that it should also be considered in terms of an omission or failure to act.

"In the active sense, collusion has amongst its meanings to conspire, connive or collaborate.

"In addition, I intend to examine whether anybody deliberately ignored a matter, or turned a blind eye to it, or to have pretended ignorance or unawareness of something one ought morally, legally or officially to oppose."

 In essence, his view is that collusion can be established by action or inaction of an individual or body.