An Aboriginal man with cognitive impairment who was wrongfully convicted over the bashing death of Broome man Josh Warneke is seeking compensation from the state, his lawyer says.

Gene Gibson spent five years in jail before his manslaughter conviction was quashed.

He was originally charged with murder in August 2012, but this was downgraded after officers bungled a police interview by not giving him the right to an interpreter.

A Corruption and Crime Commission (CCC) investigation into the death of Mr Warneke later exposed "systemic failures" within WA Police.

Mr Gibson is from the remote community of Kiwirrkurra and barely speaks or understands English.

He argued during the appeal that he did not understand the legal proceedings and that he was induced to make a plea based on a false or unreliable statement.

His lawyer Michael Lundberg said Mr Gibson deserved restitution "to right the wrong done" to him.

"Gene has asked me to seek compensation from the Government for the time he has lost in prison and the impact that all of this has had on him and his family," he said.

Sorry, this video has expired Gene Gibson freed as conviction for Broome manslaughter quashed

He also revealed that Police Commissioner Karl O'Callaghan had travelled to Alice Springs, where Mr Gibson has been spending time since his release from prison, to personally apologise to him.

"Gene is very grateful that the Commissioner has apologised not only to Gene, but to his family," Mr Lundberg said.

The 21-year-old Mr Warneke was found dead on the side of a road after leaving a nightclub in February 2010.

Mr Gibson, 25, was sentenced in 2014 to seven-and-a-half years in jail after admitting the unlawful killing of Mr Warneke.

Josh Warneke's body was found by the side of a road in 2010.

But Mr Gibson — whose first language is the traditional desert language of Pintupi — argued he did not understand the court process or the instructions given to him through an interpreter when he entered his plea.

Testifying at the appeal earlier this year, he told the court via an interpreter that he did not kill Mr Warneke and said police had not listened to his story.

The court also heard he was advised to plead guilty after he was implicated in witness statements — and it was not until after he had done so that two incriminating witnesses recanted their evidence.

Mr Lundberg said Mr Gibson was seeking a "substantial" sum.

"We're confident the current Labor government will treat the compensation application with the right level of compassion, respect and expedition, particularly given the undeniable injustice that Gene has suffered," he said.

"Gene has spent the past few months in Alice Springs, in Kiwirrkurra and other parts of the Northern Territory and the Kimberley … with his family and friends.

"He's played football, he's been hunting and he has renewed his passion for music."

Reasons for quashing conviction outlined

The Court of Appeal today outlined its reasons for overturning Mr Gibson's conviction.

It found a miscarriage of justice had occurred based on the likelihood that Mr Gibson did not understand either the legal process, the state's case against him, the advice of his lawyers or the options that were available to him.

It accepted that Mr Gibson had cognitive impairments that affected his capacity to function in day-to-day life, make decisions of importance, understand complex instructions, remember detailed information and seek support.

Mr Gibson, the court ruled, was shy, reserved, compliant, agreeable and vulnerable to suggestions by others.

His life had been one of disadvantage, with his father dying when he was very young and his mother abandoning him.

His inability to adequately speak or understand English was also highlighted, with the judges raising doubts about the adequacy of the services provided by the interpreter who assisted Mr Gibson.

The Court of Appeal found Mr Gibson was an honest witness but his recollection of events was "adversely affected" by his cognitive impairments and lack of understanding.

