A "hypoglycaemic episode", or low blood sugar, may be the reason Shari-Lea Hitchcock, the long-time mistress of cardboard billionaire Richard Pratt, allegedly bit a police officer after a lunch out with friends last year.

Defence barrister Greg James QC requested the socialite's case be heard under Section 32, a clause usually reserved for offenders suffering a mental health disorder.

Hitchcock, who is facing three charges of common assault, assaulting police and resisting arrest, was attended to by a passerby who saw her walking in the middle of Oxford Street on a busy Friday afternoon last year. Police arrived and she was accused of putting up a "short struggle", biting and kicking a police officer in the process.

"They formed a view that obviously she appeared disoriented, irrational and intoxicated," Mr James said. "It appears however, the facts immaterial, that condition seems to be generated by her weight, the work she had been doing and her limited amount of food she had ingested over the previous 24 hours."

Hitchcock, prior to the altercation, had been lunching with friends including her daughter Paula, 19, and Lizzie Buttrose, niece of Studio 10 star Ita Buttrose, at the upmarket Woollahra eatery, The Centennial.

Mr James told Magistrate Michael Barko the 47-year-old had eaten lunch but "hadn't appeared to have eaten very much". She also drank "two glasses of alcohol".

"She was obviously affected by the condition which is described as a hypoglycaemic episode," he said.

Mr James explained that her brain was "deprived of glucose" which led her to acting irrationally.

Hitchcock had suffered from the same condition previously and experienced amnesia and blackouts from working too hard, Mr James added.

The defence team also provided Magistrate Michael Barko with published research of her alleged condition.

"It's always refreshing to look at a book rather than the internet," Mr Barko said.

Hitchcock was supported in court by a friend and the pair appeared confused when Mr James outlined how Hitchcock was suffering a mental condition at the time of her arrest.

"What's he talking about?" the friend asked Hitchcock.

Hitchcock pleaded not guilty and appeared in court wearing a black and floral ensemble, and carrying a Guess handbag and large takeaway coffee.

Four witnesses will be called to give evidence and a professor specialising in hypoglycaemia will be cross-examined at Waverley Local Court on Tuesday afternoon.