A couple have been jailed for nine years for abusing a 17-month-old boy who was sliced with a knife and burned with cigarettes.
Ikram (l) and Parveen protested their innocence
Sumairia Parveen abused stepson Tahla Ikram before his death in September 2006, Southwark Crown Court heard.
Parveen, 24, and the child's father Abid Ikram, 31, from west London, were convicted of causing or allowing the child's death at an earlier hearing.
Ikram received a further 12 months for perverting the course of justice.
The child's many wounds included a broken thigh and shin and three fractured ribs, the court heard.
His injuries were ignored for days, causing him to scream as his broken bones ground together.
The couple, from Ealing, spent more than a week during the trial protesting their innocence.
Ikram told the court he "would never have hurt" his son while Parveen insisted she had loved Tahla as if he "was my own".
Judge Nicholas Loraine-Smith said the final assault on the boy, breaking a leg that had already been fractured, "must have been a brutal attack".
He told the pair: "You both know what really happened, and to protect yourselves and each other, have chosen not to tell the truth about it."
They were convicted of the "causing or allowing" offence, which does not require the individual who inflicted the fatal blow to be identified.
Both were banned for life from working with children and Parveen was recommended for deportation after her sentence.
After the hearing, Det Insp Colin Welsh said: "This is one of the first convictions since this [causing or allowing an offence] legislation was brought in.
"No sentence can be long enough for causing the death of an innocent child by those who should have protected him."
The court heard how the boy's father stood by and did nothing while the abuse happened.
Ikram had been formally cautioned for child neglect in March 2006 after police found Tahla alone at home.
The boy was placed in foster care but within months he was handed back to Ikram. By this time, Parveen had given birth to her own child.
She moved in with Ikram after walking out on her husband but she hated Tahla who she felt threatened their relationship.
Jeremy Donne QC, prosecuting, told jurors Parveen clearly regarded Ikram's son as an "obstacle" to their affair. She began to "hate" him and then either to hurt him or allow him to be severely injured.
The court heard how Tahla was repeatedly taken to hospital, but seeing a different doctor each time probably prevented his mounting injuries being recognised as systematic abuse.
The child finally died in his cot on 6 September last year. A doctor who examined him said he looked like a car accident victim.
A post-mortem examination discovered a marrow fat embolism from the untreated broken thigh had invaded his lungs, starved his brain of oxygen and caused death.