Gaye Matthews remembers the time her daughter made a hospital doctor cry when the young physician could not understand what was wrong with her patient.
"(The hospital) wouldn't let either her father or myself go in with her and I kept going and saying she cannot speak, she can do nothing for herself," Ms Matthews said.
When she was allowed to see Charissa 45 minutes later, Ms Matthews found the doctor sitting on the bed in tears.
"I said what are you crying about and she said, 'I can't get her to tell me what's wrong."
Ms Matthews shared her experience at a parliamentary inquiry examining end of life choices and the need for voluntary euthanasia laws in Western Australia.
Charissa, who died in 2011 aged 41, had Rhett syndrome, a genetic neurological disorder which reverses a person's development between six to 18 months of age.
Ms Matthews said many people, including doctors, devalued her daughter as a person because she was unable to speak, feed herself or move.
"I think on the part of doctors there's ignorance on the understanding of the being of a person," she said.
IdentityWA chief executive Marina Re told the inquiry the group feared people with a severe intellectual disability could be made vulnerable under laws which allowed voluntary assisted deaths.
The service provider supports about 150 people with a disability to live independently.
"The decision (to access voluntary assisted dying) would rest in the hands of others, and in some cases, those others may have limited exposure to people with disabilities or understanding of the health complexities faced on a daily basis," the group said in its inquiry submission.
"The involvement of people who know the individual well is absolutely paramount," Ms Re said.
"My feeling is very much that people with a serious intellectual disability just cannot be put into that position," Ms Matthews said.
The Joint Select Committee inquiry is set to hear from the Australian Medical Association and Catholic Healthcare Australia on Wednesday.
