Defenceless two-year-old Liam Fee died at his home near Glenrothes, Fife, on March 22, 2014 after suffering heart injuries similar to those found on road crash victims.
His mother Rachel Trelfa or Fee, 31, and her partner Nyomi Fee, 29, tried to pin the blame for the death on a young boy but were convicted of Liam’s murder in May following a seven-week trial at the High Court in Livingston.
The pair - originally from Ryton, Tyne and Wear - were also found guilty of a catalogue of horrific cruelty against two boys in their care, including the one they blamed for Liam’s death.
Sitting at the High Court in Edinburgh, judge Lord Burns handed both women mandatory life sentences.
He ordered Trelfa to serve a minimum of 23-and-a-half years behind bars, while Fee must spend at least 24 years in prison before she can even be considered for release.