Fatal breast procedure was a 'mistake,' jury told

The 35-year-old agreed to the procedure believing Shao was a doctor, crown prosecutor Sara Gul said as a criminal trial began at Sydney's Downing Centre District Court on Thursday.

"She ended up dead," Ms Gul said.

Shao was grossly negligent to a criminal degree, the court was told. (Dan Himbrechts/AAP PHOTOS)

Ms Huang died on September 1, 2017 after the procedure - which was not legally allowed in Australia - involving hyaluronic acid being injected directly into her breasts as filler.

A local anaesthetic was administered after Ms Huang expressed concerns about how painful the procedure would be, the jury heard.

Neither the hyaluronic acid, anaesthetic nor a painkiller injected into Ms Huang were approved for use in Australia, Ms Gul said.

Things went "to hell in a handbasket" because too much anaesthetic was used, the prosecutor said.

"Some time after the (anaesthetic) was injected, Ms Huang started twitching, started convulsing, started foaming at the mouth, effectively lost consciousness and she had a cardiac arrest."

The clinic did not have trained staff, resuscitation equipment or emergency drugs required to perform this type of cosmetic surgery, the barrister said.

While paramedics attending the scene after a triple-zero call were able to restart Ms Huang's heart, the 35-year-old was pronounced brain dead in hospital and her life support turned off.

Despite the anaesthetic having "disastrous effects" if it entered a vein, Shao injected it into Ms Huang's breasts via a surgical tube inserted through a slit in the skin cut open with a scalpel, Ms Gul said. 

Shao had engaged in the unlawful act of injecting Ms Huang with a dangerous dosage of anaesthetic that exposed her to serious injury, she told the jury.

The Chinese national was also grossly negligent to a criminal degree and had breached a duty of care owed to her patient through the cosmetic procedure, she added.

The 40-year-old has pleaded not guilty to manslaughter for the unlawful killing of Ms Huang but has pleaded guilty to injuring her by administering a poison.

One of the witnesses giving evidence against Shao is Caroline Fu, an unregistered nurse working at the Medi Beauty Clinic.

She mixed up the painkillers and anaesthetic, providing it to Shao at the time of the fatal procedure.

"It's not manslaughter. It's a terrible mistake. Mistakes, plural." Winston Terracini (right) said. (Dan Himbrechts/AAP PHOTOS)

Fu pleaded guilty to one count of administering a poison and has received a discounted sentence of a community corrections order and conditional release order in exchange for giving evidence in Shao's trial, the jury heard.

Shao's barrister Winston Terracini SC said Fu was responsible for mixing up the drugs before handing them to his client.

"That's a real issue in the case, who mixed up the (anaesthetic) and the other sedative opiate drug that you've heard about."

He likened what happened to accidentally putting diesel in a petrol vehicle, saying that Shao had merely made a "mistake".

"It's not manslaughter. It's a terrible mistake. Mistakes, plural," he said.

"Errors of judgment can be made in life."

The only registered doctor in the clinic went straight to the airport after the incident, Mr Terracini said.

"You won't be hearing from him because he won't come back from Taiwan," the jury was told.

Mr Terracini urged jurors to avoid doing their own research on the "Google machine" or getting their own "bush lawyer advice" from family members.

"All deaths are tragic but they're more tragic sometimes when people die young, so do your best with that," he said.

The hearing continues on Friday.