Ann Marie Smith's former friend tells disability royal commission of caring young woman who loved to laugh

Police believe Ann Marie Smith, pictured celebrating her 21st birthday, may have spent up to a year confined to a chair before she died in hospital. (Supplied)

A childhood friend of Ann Marie Smith has remembered the Adelaide woman as a caring person who loved to laugh and was cherished by her family.

Senior counsel assisting Kate Eastman SC read out a letter from a woman only identified as "Brooke" at the Royal Commission into Violence, Abuse, Neglect and Exploitation of People with a Disability sitting in Adelaide on Wednesday.

Ms Smith, who was known as Annie, died last year from severe septic shock, organ failure, severe pressure sores, malnutrition and issues connected with her cerebral palsy.

Police believe the 54-year-old may have spent up to a year confined to a cane chair before she died in hospital.

Her carer has been charged with manslaughter.

This photo of Ms Smith at school was one of the images shared at the royal commission. (Supplied)

Brooke first met Ms Smith when they were nine and seven respectively.

"Sometimes she would start laughing for no apparent reason. I may have tripped or done something silly and off she would go."

Brooke said Ms Smith, pictured with friends, used to love dancing to ABBA songs. (Supplied)

Photographs of a younger Ms Smith were shared with the commissioners.

"I remember she would get up and jig along whenever an ABBA song came on," Brooke wrote.

"She was always dressed in nice clothes and she used to get her hair done in a salon."

But the inquiry heard she increasingly shut herself off from the outside world.

After decades of sharing special events, the friends had a falling out and did not speak in the year before Ms Smith died.

"I know that things would have been different if I had gone around to see her," Brooke wrote.

The statement was read as the inquiry turned its focus to authorities' response to Ms Smith's death last April.

Photographs of a Ms Smith were shared with the commissioners. (Supplied)

'Not a proper and competent  investigation'

Also today, South Australia's Department of Human Services admitted it did not do enough to investigate an anonymous letter threatening violence against a group home resident.

The royal commission heard the letter threatened the man might be poisoned or fall down stairs, but his family was told to move on when they raised concerns.

The department's internal audit manager, Tony Allwood, admitted the reports it did on the issue were defective.

"Yes, yes," Mr Allwood agreed.