Hamzah Khan’s body, still dressed in a tiny babygro made for children four years younger than him, was found buried under other items in a discovery which “disturbed even hardened” police officers.
He had been starved to death, it is alleged, and was so malnourished he fitted into clothing designed for babies aged between six and nine months.
Hamzah’s mother Amanda Hutton, 43, a former care assistant, denies manslaughter.
Her trial at Bradford Crown Court heard that police searched her home after a community support officer became concerned about the smell coming from inside.
Paul Greaney QC, prosecuting, told the jury that once inside they found Hamzah, who died on December 15 2009, aged four-and-a-half.
"Hamzah's growth had been stunted," Mr Greaney said. "It had been stunted because he was malnourished over a lengthy period and that state of affairs resulted in his death. In short, he starved to death.
"How had a child starved to death in 21st century England?"
The alarm was raised in September 2011 by police community support officer Jodie Worsley, the jury was told, who spoke to Hutton and became concerned about the smell coming from her house in Bradford, West Yorkshire.
She called in back up and the team of officers who began searching the property were met with "conditions of squalor".
"What they discovered disturbed even hardened officers," Mr Greaney said.
It was in Hutton’s bedroom that police officer Richard Dove made the “dreadful discovery”.
"Within a cot, beneath other items, he found the mummified corpse of a child," Mr Greaney said.
The jury heard that Hutton abused alcohol and cannabis, and were told they would have to consider whether Hamzah "became a secondary and less important consideration than those addictions".
The defendant used to work as care assistant and there is evidence that she has undergone some first-aid training, it was said.
Her lawyers are expected argue that Hamzah's malnutrition could have arisen through "some naturally occurring condition".
But Mr Greaney told the hearing that Hutton was guilty of manslaughter by gross negligence on two grounds – that she failed to feed him adequately and failed to seek medical assistance for him.
He added: "Amanda Hutton failed to provide her child with the nourishment that he needed to survive and, in so failing, she killed him."
Hamzah's father, Aftab Khan, was separated from Hutton and lived elsewhere.
Mr Greaney said there is evidence that he was violent towards the defendant.