The 35-year-old admitted to carrying out New Zealand’s deadliest modern day mass shooting before being sentenced to life in prison in August 2020.

He appealed to the Court of Appeal in February, saying “torturous and inhumane” detention conditions during his trial made him incapable of making rational decisions when he pleaded guilty.

“This Court does not accept Mr Tarrant’s evidence about his mental state,” the court findings said.

“There were inconsistencies in Mr Tarrant’s own evidence, and his evidence is at odds with the detailed observations of prison authorities and the assessments of mental health professionals at the time of him entering his pleas.”

The panel of three judges found Tarrant’s guilty pleas were voluntary, and “he was not coerced or pressured in any way to plead guilty”.

“The evidence overwhelmingly demonstrates that he was not suffering any significant psychological impacts as a result of his prison conditions at the time he pleaded guilty,” the court said.

The court said Tarrant’s “proposed conviction appeal is utterly devoid of merit”.