Damian Eric Maxfield (40) who was due to stand trial in Perth, pleaded guilty at the last minute to three charges including murder, which he committed during a home break-in in Halls Head last year.
Maxfield’s trial was to be before a judge alone in the Supreme Court of WA on Monday.
He was accused of stabbing 40-year-old Scott Martin to death and seriously injuring his partner Erelle Mason (32), while the pair were in bed in their apartment in January last year.
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READ NOWAt the time police claimed that Mr Maxfield hit Ms Mason in the face with a brick while she was sleeping.
Maxfield instead pleaded guilty to murder, aggravated burglary, and doing an act likely to endanger the life, health or safety of a person.
The latter charge was downgraded from attempted murder on a public interest basis, Prosecutor Laura Christian said.
Maxfield showed no emotion when he entered his pleas, but there were tears in the packed public gallery.
Maxfield, who broke into the property while Mr Martin and Ms Mason were asleep, will face a sentencing hearing on Thursday.
Justice Michael Corboy will decide in the meantime whether the victim’s mother Carol Martin can read out her victim impact statement in court.
According to a crowdfunding page that was created the day after the crimes, the couple lost their three-week-old boy Mason to SIDS three years ago.
Ms Mason’s family said money fundraised went into a trust in the name of Ms Mason and Mr Martin’s dead son Mason.
Money from the trust went toward Ms Mason’s physical and psychological rehabilitation. More than $10,000 was donated.