An infertile woman who was the "key architect" behind the murder of an intellectually impaired woman, so she could take custody of her four children, has been jailed for 30 years.
Christine Lyons, 47, previously had a hysterectomy but desperately wanted children of her own.
She had asked a number of women to have children for her, but no one had agreed.
Finally, she put together a "heartless and thoroughly evil" plan to send 39-year-old Samantha Kelly "on a permanent holiday", with the aim of taking custody of the victim's children.
Both Christine's current partner, Peter Arthur, and former partner, Ronald Lyons, were "so devoted" to her that they wanted to help her achieve her objective.
The trio lived together along with Ronald's three children, with Ms Kelly living in a bungalow at the back of the Bendigo home.
On January 20, 2016, Christine and Ronald Lyons fed Ms Kelly a "cocktail" of sedatives, beta-blockers, anti-nausea tablets, analgesics and antihistamines.
Ms Kelly felt groggy but did not die.
Then on the night of January 22 or the early hours of January 23, Christine directed Arthur to kill Ms Kelly with an "alternative method".
Arthur then went to the bungalow and struck Ms Kelly with "extreme force" to the head with a hammer about seven times.
Ronald bought two shovels from Bunnings and accompanied Arthur on a trip to dispose of Ms Kelly's body.
After Ms Kelly's disappearance, Christine renamed two of her children to names she'd always wanted to call her own children, and enrolled them in a new school.
The trio told police Ms Kelly had left in the middle of the night and "no longer wanted to care for her children".
"Samantha was a loving, devoted and caring mother," Justice Stephen Kaye said during sentencing on Thursday.
"The motive of each of you to take from her, her four young children, by depriving her of her life was heartless and thoroughly evil."
Christine Lyons, who was convicted of both attempted murder and murder, will spend at least 23 years in jail before being eligible for parole.
Ronald Lyons, 46, who is unrelated, was jailed for 12 years, with a non-parole period of nine years, for attempted murder and assisting an offender.
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