A three-year-old boy was fatally crushed by a car passenger seat pushed back by his mother's boyfriend who felt he was being too noisy, a court heard.
Alfie Lamb went "ominously quiet" after he was deliberately squashed in the vehicle, the court heard.
His mother, Adrian Hoare, 23, allegedly lied to police, telling them Alfie was in a taxi when he became unresponsive after falling asleep, in February 2018.
She and her boyfriend Stephen Waterson deny manslaughter at the Old Bailey.
Mr Waterson, 25, who was in the front passenger seat, allegedly pushed his seat back twice in anger at the "noise and fuss" Alfie was making in the rear footwell of the Audi, which was being driven by his acquaintance, Marcus Lamb.
Ms Hoare, who lives with Mr Waterson in Adams Way, Croydon, was in the rear seat, sitting above her son.
Duncan Atkinson QC, prosecuting, said a pathologist found the "smiley boy" died from crush asphyxia.
"It was caused by the front passenger seat of the Audi vehicle, Waterson's seat, being moved back further into the rear passenger side footwell at a time when, as was known, Alfie was in that footwell," Mr Atkinson said.
"In effect, he was squashed by the car seat and suffocated. This movement of the seat was a deliberate action by Waterson who knew that Alfie was there and was angered by the noise and fuss that the three-and-a-half-year-old was making during the fateful car journey.
"The deliberate movement of the seat, by electrical operation by the touch of a button and involving the application of considerable force to Alfie, took place not once but twice."
Mr Atkinson said Mr Waterson moved the seat forward when others in the car realised it was causing Alfie to have breathing difficulties.
"However, when Alfie made noise again, Waterson deliberately moved his seat back again, and kept it in that reversed position, squashing Alfie, as he again showed signs of breathing problems until he went ominously quiet," he said.
Ms Hoare had a duty of care to Alfie but did "nothing" to help him, Mr Atkinson added.
Despite Mr Lamb trying to resuscitate the child, it was obvious to police and medics that Alfie had been dead for some time when they were called to Adams Way on the evening of 1 February, Mr Atkinson said.
Ms Hoare allegedly told paramedics Alfie had fallen asleep in a taxi, but was unresponsive when she tried to wake him.
Mr Atkinson said this was "only the beginning of the lies that she, and others, were to tell".
Police found CCTV footage of Ms Hoare, Mr Waterson, Mr Lamb and his then-girlfriend, Emilie Williams, in a dark Audi car.
Since then Miss Williams had been attacked by Ms Hoare, and Mr Lamb intimidated by Mr Waterson, the court heard.
Mr Lamb, 22, and Miss Williams, 19, are due to give evidence against the defendants.
Ms Hoare denies manslaughter, child cruelty, and common assault on Miss Williams.
The couple and Miss Williams have admitted conspiring to pervert the course of justice by making false statements to police.