A 17-month-old toddler died after enduring months of torture and "extreme pain" inflicted by his father and his lover, a court has heard.
Tahla Ikram suffered fractures, bruises and a cut on his leg which revealed his "tendons and blood vessels".
Abid Ikram, 30, and Sumairia Parveen, 24, of Cheltenham Place, Ealing, London, deny murder and causing the death of a child.
Mr Ikram had been formally cautioned for child neglect in March 2006.
Southwark Crown Court heard Tahla was then handed back to Mr Ikram after a few weeks in foster care.
The child was found cold and stiff at the family home in Acton, west London, last September by an ambulance crew. He was pronounced dead at hospital soon after.
Jeremy Donne, QC, prosecuting, said the crew noticed Mr Ikram appeared distressed but Ms Parveen was "quite calm".
A post-mortem examination found a broken thigh, shin and three fractured ribs and concluded marrow fat deposits from the fracture had invaded his lungs.
They, in turn, deprived his brain of oxygen, resulting in his death.
Mr Donne said: "So the broken thigh killed Tahla and whoever broke Tahla's thigh killed Tahla."
The court heard that every time Tahla was taken to hospital the accused gave different explanations for injuries and saw different doctors.
The couple told friends they left him alone at home on many occasions, prompting one friend to alert authorities, resulting in the child being placed in foster care.
Mr Donne said Tahla "thrived and flourished" with the foster family.
"With them he learned to walk and began to say his first words", but was soon handed over to his father in a "fateful decision", he added.
In August, carers advised the child be taken to hospital after they found him unable to walk and dazed.
The doctors put Tahla's broken leg in a cast, but the couple kept returning to hospital complaining the cast kept coming off.
During one such visit a doctor noticed a cut behind his knee, which after Tahla's death was found to be much deeper "revealing tendons and blood vessels."
The trial continues.