Recent autism diagnosis of convicted killer Alan Hall raises doubts over guilt

New evidence in the bid by convicted killer Alan Hall to clear his name can be revealed by Newshub.

The 58-year-old was jailed for murdering Auckland man Arthur Easton in 1985.

Last year, Hall was diagnosed with autism and now his defence has an expert report which could throw doubt on his guilt.  

To police, Alan Hall was a man without an alibi or remorse; a suspect with inconsistent stories about how his hat and bayonet ended up being used to kill Easton.

Defence investigator, Tim Mckinnel, says prosecutors at Hall's trial said his behaviour was evidence of guilt. 

"Some of the ways he behaved and responded to police questions is really quite unusual. We now know after 34 years that Alan is in fact, autistic." 

The defence has a new report from a psychologist specialising in Autism. 

It says Hall's spectrum-disorder could have affected his ability to provide a consistent alibi and account of what happened to his bayonet and hat.  

Hall first told police he's lost the items, then claimed they'd been stolen.

"It has an impact on certain parts of a person's memory. And it seems to us like a reasonable explanation for some of the memory gaps," McKinnel said. 

The report also says Hall's condition could explain why he appeared emotionless to the jury - a trait Katie Maras is familiar with.

"So an autistic person might feel emotional, but not necessarily display it in their facial expressions," the senior psychology lecturer told Newshub. 

Maras has conducted mock trials to see how a jury's perception of a defendant's culpability changes when they learn he has autism.

"So when they were told about his autism, they were more likely to find him not guilty." 

And if they weren't told of his autism, they were more likely to misjudge the defendant's behaviour.

"I guess that they can misattribute these behaviours to be more guilty. Not having any remorse for their actions." 

For Mckinnel, Hall's case is similar to another he worked on. Teina Pora was diagnosed with foetal alcohol spectrum disorder decades after falsely confessing to murder. 

"Looking at Alan's case and the way he was dealt with by the criminal justice system, I think that this diagnosis will be at least as important as Teina's FASD diagnosis," McKinnel said. 

Behaviour once interpreted as evidence of guilt will now be used by Hall's defence team - to argue his innocence.