A man who left a two-month-old baby badly brain-damaged suggested a toddler could have caused the injuries.
Neil Kirton, 29, hurt the tiny boy while apparently feeding him late at night.
The child was rushed to hospital on July 6, 2020, looking pale and having not taken his feed.
A judge heard how medics concluded the youngster's injuries were "consistent with shaking and/or strangulation" of the baby.
Kirton went to his labourer job after attacking the child at his home in Airdrie, North Lanarkshire.
He later gave a number of statements to police making a string of claims as to what happened.
Prosecutor Chris Fyffe told how this included him alleging: "He said he did not know any reason as to why the baby would have a bleed on the brain.
"He said that he 'could only suggest (a 20-month old girl) being a bit rough with the boy in cuddling him'."
But, Kirton is now behind bars after he pled guilty to assaulting the baby to his severe injury, permanent impairment, and to the danger of his life.
He had initially faced an accusation of attempted murder.
A sobbing Kirton had his bail removed and was remanded pending sentencing.
The High Court in Glasgow heard how the boy's mum had moved into Kirton's home along with her children days before the crime.
On the morning of the attack, Kirton got up to give the baby a night feed.
But, within an hour, he woke the child's mum to ask if the boy was "alright".
Mr Fyffe said: "The assault took place at some point after Kirton removed the baby from his Moses basket."
Unaware of the horror, the mum thought her son may just be "sleepy".
Kirton put the child back in the Moses basket.
Around 7am, Kirkton took the mum and son to another woman's house on his way to work.
It was there the alarm was then raised as the ill baby was cold, pale, and still not feeding.
The mum initially contacted her GP, who was so concerned he ordered the baby to be taken to Wishaw General Hospital.
The boy went on to suffer a number of seizures.
Mr Fyffe said an "abusive head injury" was suspected due to a life-threatening brain bleed.
The baby was also found to have several suspicious "pin-prick bruising" at his neck area.
Doctors concluded these markings were "suggestive of inflicted trauma".
Mr Fyffe: "A devastating lack of oxygen to the brain can be caused if the neck is injured, squeezed of there is strangulation by forceful handling."
The court was told Kirton has not given an explanation as to how the injuries occurred and is apparently "unable to fully recall what happened".
However, he made a series of claims while being quizzed by police shortly after the attack.
Kirton said he could have been "heavy-handed" as he was not used to "being around a young baby".
In another statement, he remarked hearing a "hard knock" after putting the child onto his changing mat.
He added: "This is all my fault. It has been on my watch."
Kirton was also said to have told his boss the boy had been restless during the night, but thought it was because he had turned the heating off.
The court was told the boy has a weakness on his left side and it remains unknown how "significant" that will be.
But, the signs the boy will be able to live a "normal life" in the future fortunately remain "positive".
Lord Arthurson told Kirton: "You have pled guilty to an extremely grave offence.
"Standing that, custody is inevitable. Your bail will be revoked."
Kirton will be sentenced on May 10 in Edinburgh.
