Dyson Heydon to reveal his commission fate

WHAT WILL ROYAL COMMISSIONER DYSON HEYDON DO?

THE BACKGROUND

* Former High Court judge Dyson Heydon was appointed to oversee the royal commission into trade union corruption in March 2014.

* In April 2014 he accepted an invitation to give the August 2015 Sir Garfield Barwick address.

* On August 13 2015 he pulled out of the event after realising it was organised by the Liberal Party and the commission was continuing after an extension.

* He has since admitted he "overlooked" the connection to the Liberal Party and the timing of the speech.

* Unions and federal Labor want Mr Heydon to stand down.

WHAT THE UNIONS ARGUE

* The ACTU (on behalf of other unions), CFMEU and AWU have all made submissions seeking to have Mr Heydon disqualified.

* They claim an average person would think the commissioner would not bring an impartial mind to proceedings, having been willing to speak at a Liberal Party event.

* Mr Heydon could not give unions or other witnesses before the commission a fair hearing because of a perceived political bias, they say.

WHAT DYSON HEYDON HAS TO DO

* Mr Heydon will have to make a decision on his own future as commissioner.

* Unions want him to put himself in the shoes of a fair-minded observer when coming to his decision.

* He's spent the weekend considering what he called an "interesting and in some respects complex matter" and is due to reveal his judgement on Tuesday morning.

WHAT WILL HAPPEN NEXT

* The federal government has indicated it will want to continue with the royal commission regardless of what Mr Heydon decides.

* The commission, which was extended late last year, is due to hand down its final report by December 31.

(Source: Trade union royal commission website)