The general practitioner was accused of unlawfully killing Chan by gross negligence, through breaching a duty of care she owed to the woman, by performing an injection without obtaining proper consent and ensuring the blood product infused was properly handled and free of contamination.

Chan died a week later on October 10, 2012 of multi-organ failure and septicaemia as a result of Mycobacterium abscessus, bacteria later found on the pipette guns and centrifugal machine that handled her blood in the laboratory, Asia Pacific Stem Cell Science.

A different jury had failed to reach a verdict in Mak’s case while convicting her two co-defendants – her boss Dr Stephen Chow Heung-wing, 65, and technician Chan Kwun-chung, 34 – of manslaughter in the 2017 trial, also presided by Madam Justice Judianna Barnes.

Chow, who introduced the unproven treatment to customers of his beauty empire DR Group, is serving 12 years in prison; while Chan, the laboratory technician who handled the blood products without conducting any bacteria tests, is serving a shorter term of 10 years.

Both men are appealing against their conviction and sentence, while Mak’s case had already gone to the top court last year for clarification on what prosecutors must prove, to establish the death was caused by gross negligence on the defendant’s part.

Doctors are rarely found guilty of manslaughter, an offence punishable by life in prison, in Hong Kong.

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The convictions were the first of their kind in the city’s vast, largely unregulated industry of beauty treatment clinics that have offered everything from stem cell injections to body contouring surgery.

In 2012, four women fell seriously ill after receiving cytokine-induced killer (CIK) cell therapy injections at DR Group’s Hong Kong Mesotherapy Centre in Causeway Bay.

The treatment, sold at HK$59,500 per injection, was promoted as a way to improve immunity by enhancing the CIK cells in the body that are capable of killing their mutated counterparts before they become cancerous.

The process involved drawing blood from the customer, for it to be cultured in the laboratory for proliferation of CIK cells, before being injected back into the body.

At trial, Bruce said the treatment might conceivably be used by advanced cancer patients who were running out of options, but “should never have been done” on healthy people such as Chan when its effects were unproven and uncertain.

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The prosecutor also observed that contamination was a fundamental risk of the treatment but that there were “lamentable failures” in how the laboratory had handled the blood products.

Defence counsel Peter Duncan SC had urged the jury to consider his client’s conduct from the perspective of a young doctor in the relatively early stage of her career.

Mak had testified that she believed the treatment was safe, without much side effects, and that it could be beneficial to healthy people, based on what she learned on a trip to Guangzhou and in studying various literature on the subject.

She also said she believed the laboratory had carried out sterility tests so it never occurred to her that the blood products would be contaminated.

The court heard Mak had administered the treatment to more than 20 customers without incident before Chan fell ill.

The source of bacteria was never identified because of the lack of protocol and documentation at the laboratory.