The doctor responsible for a beauty treatment that killed a patient and seriously harmed two more was jailed for three and a half years Tuesday for gross negligence.

A Hong Kong court found Dr. Mak Wan-ling, 39, guilty of manslaughter last week for her role in the 2012 death of Chan Yuen-lam, 46, after receiving a $7,000 blood infusion at Mak's clinic in Causeway Bay.

"If she had done her job, this wouldn't have happened," Madam Justice Judianna Barnes said during the trial last week. "She failed her job of being the last defense to protect the patient."

The fatal treatment had been marketed as a way to improve immunity - blood was taken from a patient and cultured in a lab before being reinjected into the body.

But Chan's sample was tainted by mycobacterium abscessus bacteria on laboratory equipment which, over the following week, caused organ failure, sepsis and ultimately death. Two other women patients were injected with contaminated blood but have since recovered.

The incident was "obviously a terrible error judgement," explained the doctor's counsel Peter Duncan, who said Mak was "seriously affected by the consequences" of her actions and had lost career prospects as a result.

As mitigating factors in her use of contaminated equipment, Duncan said Mak's clinic had low regulatory standards and Mak trusted her employer Dr. Stephen Chow Hueng-wing, 65, and laboratory technician Chan Kwun-chung, 34 - who also stood trial for the same charge in 2017 and received 12 years and 10 years in prison, respectively.

Chow developed the still-unproven treatment to be sold at his once lucrative DR Group wellness brand outlets. His sentence, and those of his former employees, was a rare example of Hong Kong doctors being found guilty of manslaughter.

While Mak was also charged in the 2017 case, a High Court jury failed to reach a verdict - resulting in the now concluded retrial.