The Morris tribunal has made a formal order to seek the assistance of the High Court following the refusal of a former garda to give evidence.
Martin Leonard, who was dismissed from the force last year, earlier told chairman Mr Justice Frederick Morris that he had no confidence, and "absolutely no respect" for the tribunal and would not answer any questions.
"I know that you will go to your High Court and make your application," he said, before leaving the stand.
Mr Leonard said the tribunal was "an exercise in public humiliation", and that the tribunal had refused to accept any evidence he had given on previous occasions.
"The most shameful thing of all chairman, is that you accused my wife of lying, and that's inexcusable," he said. "The tribunal has rendered my evidence as meaningless and worthless, and useless."
The chairman said it was his function to tell the truth as "it's a matter of regret to me if it harms the people on whom I report".
"With regard to what you say about your wife's position, my recollection is that I addressed your wife in the terms that she was a decent lady that was caught up in the intrigue that was going on around her. And those in my view are the correct words to summarise what the position was."
After a short recess to allow Mr Leonard to consider his position, the tribunal resumed. The chairman said that since Mr Leonard had departed, he was making the formal order.
Earlier, Mark McConnell told lawyers for the Garda Commissioner that he would be answering their questions under protest. Mr McConnell, who was wrongly arrested following the death of cattle dealer Richie Barron, gave evidence for the third day about his treatment on three occasions when he was arrested in the 1990s.
The tribunal has found that Mr McConnell and his cousin Frank McBrearty jnr, and 10 other people who were arrested, were innocent of any involvement in the death of Mr Barron, the vicitim of a hit and run collision.
Gardaí deny Mr McConnell's allegations that he was verbally and physically abused and shown postmortem photographs while in custody.