Entering a court can be daunting for just about anyone, but carries more confusion and risk for those with an intellectual disability.
Defendants with intellectual disabilities can be at risk of false imprisonment, longer sentences and lack of access to parole, largely because of communication difficulties.
It is hoped New Zealand Law Foundation-funded research carried out in Dunedin at the Donald Beasley Institute will lead to improvements in how the court system caters for defendants with intellectual disabilities.
Institute director Brigit Mirfin-Veitch said the research report was being used as a teaching tool for judges and lawyers.
The quashing of Teina Pora's rape and murder convictions this year made the work topical.
Mr Pora's then-undiagnosed foetal alcohol spectrum disorder is considered a factor in his false confession to the 1992 crime.
The focus of the study was defendants, but the two-year project included interviews with intellectually disabled witnesses and victims, as well as with lawyers and judges.
Lack of funding for intellectual disability research meant few evidence-based resources and detailed statistics had been produced.
Restrictions on legal aid funding since 2009 have exacerbated difficulties for those with intellectual disabilities, report co-author and University of Otago law faculty dean Prof Mark Henaghan says.
The legal aid changes restricted the choice of lawyer.
This was problematic, because not every lawyer was suited to dealing with clients with intellectual disabilities.
It was not just the time it took for lawyers to understand their client, but also about allowing the lawyer the time to smooth out court system issues for the client, he said.
Most problems related to communication.
''We can easily prejudge people who don't communicate the way we do.''
''They tend to be judged in ways that would probably be inappropriate, because when people don't communicate in ways that we expect them to, we tend to make all sorts of other assumptions about them,'' Prof Henaghan said.
Mr Pora was a ''classic example'' of a defendant failed by the system because of communication problems.
''Systems just don't seem to understand how important it is to have good communication.''
''In that one moment, you can lose your opportunity to be fully understood.''
Jail was a harsher punishment for the intellectually disabled than for other defendants, because of the toughness of the environment.
This weighed heavily on judges, who were aware of the problem and wanted more research and resources, Prof Henaghan said.
''If you're a judge you'd feel awful sentencing someone for something they may not have done, or sentencing them inappropriately when they've got a disability that you didn't quite understand,'' Prof Henaghan said.
Founded in 1984, the Donald Beasley Institute is New Zealand's only independent institute devoted to researching intellectual disability.
It is named in honour of its founder, a retired paediatrician living in Whangarei.
