Arthur Labinjo-Hughes, a six-year-old boy, was killed by his father and his accomplice.
Thomas Hughes and Emma Tustin tormented the kid, who died of a head injury in Solihull in June 2020 while in the care of his stepmother.
According to the court, Tustin shook him and beat his head on a hard surface after poisoning him with salt.
Tustin was found guilty of murder and Hughes was found guilty of manslaughter at Coventry Crown Court.
They were also found guilty of child maltreatment.