Criminal charges will be considered against prosecution witnesses who gave evidence at the inquiry into the conviction of Roseanne Catt over a conspiracy to murder her husband.

The judge heading an inquiry into Catt's convictions said he would refer evidence of more than 100 phone conversations between key prosecution witnesses to the NSW Police Commissioner and the NSW Director of Public Prosecutions to determine whether criminal prosecutions should be launched against them.

The acting District Court Judge, Peter Davidson, said at a final hearing on Friday that his inquiry, which began in February last year, was complete and he would forward his findings to the NSW Court of Criminal Appeal early this week for a decision on whether any or all of Catt's 1991 convictions should be overturned.

Catt spent 10 years in prison for possessing a pistol and poisoning, stabbing, assaulting and conspiring to kill her then husband Barry Catt. While the prosecution painted her as an evil and manipulative woman, the defence case has been that she was the victim of a conspiracy between prosecution witnesses.

The case was reopened after an acquaintance of former NSW detective Peter Thomas, who led the police investigation, provided the Attorney-General, Bob Debus, with a statement saying Thomas told him he planted a gun on Roseanne Catt.

Mr Debus then requested the Court of Criminal Appeal allow a fresh appeal in the case.

In the last days of Judge Davidson's inquiry, defence barrister Tom Molomby, SC, succeeded in tendering phone records of numbers associated with key prosecution witnesses, including Thomas, serving NSW detective Carl Paget, Barry Catt and his daughters.

Mr Molomby's analysis of the records showed phone contact between these people on more than 100 occasions during the hearing despite warnings from the judge they should not discuss the case or speak with anyone likely to be giving evidence in the inquiry.

Judge Davidson said the evidence of contact was so extensive further investigation was needed.

Originally published in the Sydney Morning Herald.