An Australian Federal Police (AFP) employee has been refused bail over the alleged manslaughter of his mother, who prosecutors say suffered an "undignified and agonising death".

Phillip Joseph Thompson, who is also a former New South Wales Police officer, and his brother David Thompson were charged with the manslaughter of their mother in September last year.

Court documents allege their 73-year-old mother Shirley Thompson was bedridden and "lying in a state of filth" when paramedics attended the family home last year.

The trio allegedly lived together in Greystanes in Sydney's west.

On Thursday, a hearing at Fairfield Local Court was told Ms Thompson had developed serious bed sores that had in turn caused blood poisoning.

She presented to Blacktown Hospital severely dehydrated and malnourished and, despite efforts by hospital staff, died a week later in the Palliative Care Unit.

Police prosecutor Sergeant Lachlan Kirby told the court the woman suffered "a very undignified and agonising death".

"The victim was suffering from bruising to the hips and legs, laying naked in bed on a urine-soaked towel," court documents say.

"The victim had faeces covering her bottom and several large ulcerated pressure sores."

A court sketch of David Thompson, brother of Phillip. ( ABC News: Vincent de Gouw )

In the ambulance on the way to hospital, the paramedics asked Mrs Thompson if her sons washed her.

"'When was the last time you had a shower?' The victim replied, 'I don't know'," court documents state.

"When asked 'Does your son clean your bed, does he give you a cloth?' The victim replied 'He just gives me a cloth and asks me to do it myself'."

Court documents state that when police searched the family home, "The mattress [Mrs Thompson lay on] was in such a state it could not be further examined or seized by police as an exhibit as it presented a biological hazard".

A medical report quoted in court documents found Mrs Thompson "would have been bed bound in abhorrent conditions for at least two to three weeks prior to her hospitalisation".

"Furthermore, it is very likely the victim had very limited fluid and/or food intake possibly also for a two to three week period," the report said.

Court documents say the two men inherited almost $1.5 million following their mother's death.

But their lawyer, Michael Moussa, said the money was currently in the hands of the trustee.

Mr Moussa said the circumstances were "grey" and "sad for both brothers but especially for Phillip".