The 42-year-old Kambah woman was in a critical condition last night with severe brain damage.

She tried to hang herself with a seatbelt on Friday in the back of a Corrective Services van taking her from the ACT Magistrates Court to Belconnen Remand Centre.

The Canberra Times has learned another female detainee was in the van with her at the time, separated by a partition, and is now traumatised after witnessing the suicide attempt.

ACT Mental Health Consumer Network spokeswoman Jane Williams said several organisations entrusted with her protection had let the woman down.

''We're absolutely appalled at the treatment this woman has been given,'' Ms Williams said. ''She's clearly been crying out for help and three services have let her down: ACT Mental Health, police and Corrective Services.''

She welcomed the ACT Government-commissioned independent reviews of the woman's care before and after the incident.

''Let's get these reviews out, let's make them public. I think it's about time the whole mental health system came under review.''

Police had taken the woman to Canberra Hospital's psychiatric unit twice in the two days before the incident after earlier suicide attempts, but she was sent away on each occasion after she was assessed as not needing to be admitted to hospital.

She was arrested early on Friday for allegedly breaching a protection order, and appeared in court that day without legal representation.

Magistrate Maria Doogan ordered the woman be marked as a ''prisoner at risk'' after she threatened to kill herself.

Ms Doogan initially granted the woman bail, but she was remanded in custody because she refused to sign her bail conditions and told the court she would breach them if released.

The magistrate also ordered the woman have a psychiatric assessment.

The woman was wearing a tear-proof top and was handcuffed with her wrists in front of her when placed in the van. She tried to hang herself during the 15-minute drive to the remand centre.

The two officers in the van did not realise until they arrived.

Although officers resuscitated her, she had already suffered significant brain damage.

The incident echoed a similar suicide attempt at the ACT Supreme Court two years ago.

A mentally ill Higgins man who was bashed by fellow prisoners begged a judge for access to psychiatric care and told the court six times he would kill himself.

The 26-year-old attempted suicide less than an hour later after being locked in a cell below the courtrooms, and broke his neck. The camera that monitored the cell had been working.

ACT Women and Prisons Group spokeswoman Deb Wybron called for urgent changes to Corrective Services' practices.

''Why is there no policy for security escorts for prisoners at risk, and does it mean that if police had transported this woman that this tragic outcome could have been avoided?'' Ms Wybron said yesterday.

ACT Police recently removed seatbelts from all vehicles used to transport detainees, and police guidelines require at least one officer to constantly monitor detainees deemed to be at risk of self harm.

Police vans have a perspex window for officers to view prisoners.

Although some Corrective Services vans provide the driver with security camera footage of the detainee compartment, the van in question did not. Instead, it had an aperture that could be opened and closed.

Mental health advocates said Canberra Hospital's psychiatric unit was notorious for turning away mentally ill people in need of treatment. Often people with mental illness symptoms were told their condition was not serious enough.

Mental Health Community Coalition of the ACT spokesman Barry Petrovski said,''People are often told, 'We can't accept you now because you're not sick enough. Come back when you're really sick.' Imagine if we applied that same logic to cancer treatment? It's perverse.''

Former Canberra Schizophrenia Fellowship president Annette Atherton said her mentally ill adult son had been turned away from the psychiatric unit several times despite her pleas for help. On other occasions he was admitted.

''My experience is that the person has to be as low as you can go before they will be admitted,'' Ms Atherton said.