The Killer Clown Fiend who bludgeoned a man to death with a claw hammer has gone to the Court of Appeal to fight a judge's processes dealing with a different set of charges.

Karl Nuku is serving life in prison with a non-parole period of 18 years for the murder of Dean Browne, 38, in Wellington in 2010.

He was part of a group calling itself the Killer Clown Fiends, who beat Browne to death in an Oriental Bay flat and then dumped his body in a New Plymouth garage. Mikhail Pandey-Johnson, the leader of the group, was also convicted of murder.

But it is separate offending that lead to today's court hearing.

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Nuku was convicted on two unrelated charges of aggravated assault and possession of a gun, but during the trial he applied for his charges to be dismissed under section 347 of the Crimes Act.

The section, which has since been repealed and instead made into section 147 of the Criminal Procedure Act, allows the court the ability to dismiss charges at any time before a defendant is found guilty or not guilty, or enters a guilty plea.

The trial judge dismissed the application and did not give reasons, a matter which lead to Nuku seeking a judicial review.

The case has gone from the High Court to the Court of Appeal in Wellington, where Nuku today made submissions on the matter. He was self-represented and appeared by audio visual link.

Nuku said the main issue was the process the judge used to dismiss the application, and the fact no judgment was given, so the decision could only be found by reading the trial transcript.

"His honour should have been under stronger obligation to give reasons as part of the court record," Nuku said.

He believed an "error of law" had been committed.

He said it was "troubling" that in 2017 there was still no rule in place that judges must give reasons.

Nuku also commented on how the Crown's case against him in the trial was not fully laid out.

"If they haven't developed their case . . . it puts me in a difficult position . . . it goes against my right to fully and frankly answer the Crown's case."

The judges have reserved their decision.

Nuku made headlines earlier this year when he petitioned for legislation to be passed to give prisoners the opportunity to make organ and blood donations, and that "long-serving/life prisoners should have the opportunity to make seminal donations to registered agencies, so as to father a child".