Keanu Williams, whose body showed 37 external marks of injury, was found dead in January 2011 at the home of his mother’s boyfriend after an ambulance crew were called to the flat in Birmingham.
Rebecca Shuttleworth was convicted of Keanu’s murder at Birmingham Crown Court.
Her former partner Luke Southerton was cleared by the jury of murder, manslaughter and causing or allowing Keanu’s death, but convicted on one count of cruelty.
Shuttleworth closed her eyes briefly, bit her lip, looked upwards and shook her head after the jury found her guilty of murder and four counts of child cruelty.
A six-month trial was told that Keanu was pronounced dead on January 9, 2011, after paramedics arrived at Southerton’s flat in Old Moat Way, Ward End.
Southerton, 32, and 25-year-old Shuttleworth, formerly of Hay Mills, Birmingham, had both denied any involvement in Keanu’s death.
The todder’s lifeless body was found by paramedics after Southerton dialled 999, claiming the boy had stopped breathing, was pale and had not been well.
Although fatal injuries had been inflicted on the boy up to 48 hours earlier, Shuttleworth did not seek medical help before the 999 call was made at 7.42pm on January 9.
It is thought Keanu, known to his family as “Kiwi”, suffered his fatal injuries after arriving with his mother to stay at Southerton’s flat on January 7.
At the start of the trial, prosecutor Christopher Hotten QC told the jury Keanu’s injuries were not an “isolated event” but had been the culmination of a long period of ill-treatment.
Shuttleworth, who faces a mandatory life sentence, was remanded in custody and will be sentenced alongside Southerton, who remains on bail, at the same court today.