A toddler's mother installed a spy camera above his cot because she was "concerned" about her partner months before he allegedly murdered her child by "shaking or throwing" him.
Paula Roberts, 41, left her son Charlie, aged one year and 10 months, in the care of her partner Christopher Stockton, 38, at her Darlington home while she went for an eye test, Teesside Crown Court heard.
Within minutes of her leaving, Stockton called 999 to report the toddler had gone "floppy".
Stockton, who was not Charlie's father, is accused of inflicting a fatal brain injury while sleep deprived after a night of playing on his Xbox and watching TV.
Nicholas Lumley KC, prosecuting, said: "In a very short time, for that's all it takes to lose one's temper, he must have assaulted Charlie by shaking or throwing him with considerable force."
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He denies murder and a charge of child neglect. Roberts is also charged with child neglect, which she denies.
Charlie suffered a number of bruises and injuries in the weeks and months prior to his death in January, the court heard.
Mr Lumley said Roberts expressed concerns to her brother about Stockton, who had known Charlie for around 10 months prior to his death, in August 2023.
The prosecutor said as August progressed, the relationship between Stockton and Roberts appeared to get "a little rocky". They stayed together "but there were tensions", he said.
At the end of that month, Roberts bought a spy camera which she hid in a potted plant above Charlie's cot.
Mr Lumley said she told her brother she was concerned about her partner and her son.
In May last year, Charlie was taken to Darlington Memorial Hospital with a number of bruises to his face, which his mother explained was the result of falls.
Mr Lumley said meetings with social services were held out of concern for the toddler but at that stage, his injuries were not thought to have been caused deliberately.
Charlie also sustained a painful injury to the base of his private parts, the court heard.
Charlie suffered a catastrophic head injury on 12 January.
Mr Lumley said: "What happened to Charlie once his mother had closed the door on him was no accident, much as it may have been quickly and bitterly regretted."
Roberts wept as a recording of Stockton's 999 call was played in court, in which he repeatedly said "come on mate" and "wakey wakey" to the little boy, who was not breathing.
Stockton had told paramedics, doctors and the police that Charlie had choked on a biscuit and he patted the child on the back and stuck his fingers down the toddler's throat.
But Charlie became "floppy" so he called 999.
The toddler died in hospital the next day and post-mortem tests on his brain found widespread bleeding.
A separate expert found bleeding within and around his eyes, the prosecution said.
The case was adjourned until Monday.
(c) Sky News 2024: Mum of toddler who died 'after being shaken or thrown' bought spy camera months before