A woman jailed for life for shooting dead her aunt and uncle lost her final appeal against her convictions for murder on Wednesday.

Former bodyguard Tsim Sum-kit also shot and wounded two other relatives in the attack in Quarry Bay Park in 2018, following a family lunch to discuss dividing up the estate of her late grandmother.

At a High Court trial in 2021, the defence failed to the convince the jury that Tsim had suffered from an abnormality of the mind which resulted in an impairment of mental responsibility.

In her latest appeal, Tsim argued that the legal requirement for a defendant to prove they suffer from diminished responsibility – if this is to be used as a partial defence to murder – infringes upon the presumption of innocence and the right to a fair trial.

But in a written judgement, a panel of five Court of Final Appeal judges said the question of diminished responsibility does not affect the presumption of innocence as it is not an ingredient of the offence a defendant is charged with, but an extenuating mitigating circumstance.

They said diminished responsibility is a factor that only comes into play if and when prosecutors have proven a defendant's guilt.

"The partial defence of diminished responsibility does not in any way reduce the burden on the prosecution to prove the elements of the offence of murder," the judges said.

"It is only when a defendant is prima facie guilty of murder that the plea of diminished responsibility becomes relevant. If the prosecution has not already discharged the onus of proving the actus reus and mens rea of murder, the defendant will be entitled to an outright acquittal on the charge of murder and the plea of diminished responsibility will have no further relevance."

Tsim had also asked the court to consider whether the requirement under the Homicide Ordinance for the defence to prove diminished responsibility is proportionate and justified, or whether offering some evidence to support the claim ought to be enough.

On this point, the judges said the ordinance has "the legitimate aim of alleviating the prosecution from an unworkable burden arising from the practical difficulties of proving a matter so personal to the accused".

They added that a number of factors support this conclusion, including "the fact mental disorders and their effects are not part of ordinary life experience of a jury [and] the fact an accused cannot be compelled to be subject to medical examination by the prosecution."