NT Police is "failing" to enact legal guidelines around questioning suspects with a disability, legal advocates have said, sparking concerns those with cognitive impairments are "unwittingly" implicating themselves in crimes.

Since the Royal Commission into the Protection and Detention of Children in the Northern Territory was held, the NT's criminal justice system has been under the microscope, but advocates fear those with a disability have not been adequately included in the response to the probe.

Last year almost 900 adults across the Territory were subject to an adult guardianship order — someone placed under such an order has been deemed unable to make decisions for themselves, and are delegated a carer.

Despite this, NT Police has no legal obligation to contact such a person's guardian if they are taken into custody and questioned, and there are no mandatory legal guidelines for dealing with suspects with a disability.

It has bred what advocates have labelled an ethical "grey area" where those with a disability are agreeing to police interviews and potentially implicating themselves in crimes, without legal representation or an understanding of their legal rights.

Safeguards 'crucial to human rights'

At the Northern Australian Aboriginal Justice Agency (NAAJA) in Darwin, prosecutor-turned-defence lawyer Marty Aust has seen some of the Territory's most vulnerable cycle through his office.

Mr Aust says lawyers are often tasked with having admissions made without legal advice thrown out in court. ( ABC News: Bridget Judd )

Those with a disability are starkly overrepresented within the criminal justice system.

"Cognitive impairments aren't always recognised at the time when somebody is charged with an offence or at the time statements are taken," he said.

"There's a lack of expertise both within the police force, but also with lawyers who are dealing with these people.

"The police will always want to put the allegations to an accused person. Almost inevitably the suspect will be interviewed in the absence of legal advice or a third party."

Mr Aust said defence lawyers often had a duty to get matters thrown out of court after suspects made admissions to offences they may not have committed, or do not understand what they are admitting to.

"They [suspects] might say things they would not otherwise say, [so] often the case is you end up with someone who is remanded in custody, who's purportedly made admissions to offences, and it becomes the duty of the defence lawyer to then get it thrown out," he said.

To mitigate the legal and ethical issues that can arise from interviewing suspects with a disability who do not have representation, states have put in safeguards, like Victoria's Independent Third Person system.

Under this model, an independent person must be in the room to advise a suspect of their legal rights before police can proceed with an interview.

They are trained to support and assist those with a disability by facilitating communication between parties, and informing authorities if they believe those being questioned do not understand the situation.

Mr Aust believes similar measures should be implemented in the NT.

"I'm not here to criticise police, but I'm also not here to make excuses for matters that are crucial to human rights," he said.

"We need a process that allows for a structure around identifying issues at a very early juncture, before they're spoken to formally on the record by police or given legal advice.

"At the very least, police and lawyers should be trained to identify these potentialities, just slow the process a little bit and make sure people are fit and able to engage in the process fully."

More oversight would benefit police, suspects: guardian

NT Police said officers received extensive training for conducting interviews with both witnesses and offenders during initial recruit training, and throughout their careers in specialist roles.

This includes the requirements of legislation and the result of case law, such as the Anunga guidelines.

"Ultimately, it is the court that decides on the admissibility of a statement or interview," Commander Kristopher Evans said in a statement.

He said officers would consult with a guardian if they were aware that a person was subject to an adult guardianship order.

Advocates want NT Police to adopt the Independent Third Person program. ( ABC News: James Dunlevie )

However, the Office of the Public Guardian has conceded there is no formal database to ensure police are made aware of whether a suspect is subject to a guardianship order.

"At the moment Legal Aid are the ones being called to deal with suspects in these situations, and they're often very busy or don't know how to deal with people with disabilities," said Patrick McGee, coordinator of the Aboriginal Disability Justice Campaign.

"All of those things play out to a situation where police can do what they want and no one questions them.

"If you tell a disabled person they did it, the one thing you can count on is that they will agree."

Mr McGee is a public guardian in the NT and has seen his own client arrested and interviewed by police without his knowledge.

He believes a third person system would protect both those with a disability and the police themselves.

"At the end of the day, the quality of the information they [police] are going to get is much better when someone is helping them communicate," he said.

"This program has been written into the operational guidelines of Victoria Police, so there's a good sort of precedent there that's replicated in various forms around the country.

"The NT is out of step by not having something like this."

Opportunity for change

The Territory's first public guardian, Beth Walker, oversees almost 900 clients in her care.

NT guardian Beth Walker wants to strengthen the relationship between her office and police. ( ABC News: Bridget Judd )

The Office of the Public Guardian was developed in response to the NT royal commission two years ago, and Ms Walker acutely aware of the overrepresentation of those with disabilities in the criminal justice system.

She wants to strengthen her office's relationship with police, to help those with a disability better navigate the various legal pathways.

"Research indicates that people with a disability are overrepresented in the criminal justice system, both as alleged perpetrators and victims of crime," she said.

"There needs to be some special arrangements in place or expertise in terms of how to deal with people with a disability."

Ms Walker conceded there was no established protocol allowing officers to determine if someone was subject to a guardianship order, but said it was an issue that could be "easily resolved".

She too said the NT should explore third person protocols.

"Of course we do have our issues with distance and accessibility, but a pool of independent people who have had some training and understand disability issues as well as the criminal justice system would be really beneficial," she said.

"I think police would also appreciate that being available too [because] I think the current process is quite informal."