A court will decide on Wednesday whether an independent inquiry into former Welsh first minister Carwyn Jones' sacking of late cabinet minister Carl Sargeant was legal.
The family of Mr Sargeant, who was found hanged at his home days after he was sacked, were granted a judicial review into the inquiry after they questioned the format of the investigation.
Judges Lord Justice Haddon-Cave and Mr Justice Swift adjourned the judicial review hearing held at Cardiff High Court in January after hearing Mr Jones had worked "behind the scenes" in setting out the investigation's protocols, contradicting his claim the investigation would remain "independent" of him.
Lesley Thomas QC, representing the Sargeant family, revealed the independent QC leading the probe, Paul Bowen, had also raised concerns about Mr Jones's involvement in setting its parameters, which included rules which would bar the family's lawyers from being able to question witnesses.
Mr Thomas told the hearing: "Mr Jones is controlling the process in which he will give evidence.
"He was involved in setting the operational protocol in a clear breach of natural justice and was acting as a judge in his own court.
"Behind the scenes he was acting as puppet master in relation to setting out how the investigation should be structured."
But Cathryn McGahey QC, representing Mr Jones, said the former first minister's actions were entirely lawful and that he was responsible for setting the parameters of the investigation by law.
The judgment will be handed down on Wednesday morning at the Royal Courts of Justice in London.
Father-of-two Mr Sargeant was found hanged at his home in Connah's Quay, Deeside, in November 2017, four days after he was sacked from his job as cabinet secretary for communities and children following claims he had assaulted women.
After Mr Sargeant's death, Mr Jones called an investigation to examine his handling of the sacking after pressure from the late Assembly Member's family and Welsh Labour politicians.
An inquest into Mr Sargeant's death is set to reopen in July.