A vengeful mistress who hacked her lover's wife and grandson to death with a pair of garden shears has been jailed for life.

The Chinese woman murdered the four-year-old boy as he slept - a crime the judge condemned as 'horrendous' and 'unbelievable'.

Behind the sweet smile of Cai Xia Liao is a mistress-turned-monster.

She was so consumed by romantic rage that she went to the home of her lover, Brian Mach and drugged, bound and gagged him.

View photos Cai Xia Liao. Photo: AAP More

View photos Cai Xia Liao in court. Photo: 7 News More

She took a pair of garden shears and, in a frenzy, attacked Brian's four-year-old grandson, Alastair, as he tried to defend himself in his bed.

Liao lay in wait until her lover's wife, Mai Mach, returned home and attacked her with the same weapon.

View photos Brian Mach, his wife and their grandson before the shocking crime. Photo: 7 News More

Supreme Court Justice Lex Lasry said: “You then went back into the lounge room and showed Brian Mach the garden shears and told him, quote, ‘I used these’.





“I've killed everyone to make you suffer.”

Liao, 45, was furious that, despite their three-year affair, Brian had repeatedly refused to end his marriage.

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