Several experts told the court that the injuries matched to that of movement involving "acceleration and deceleration" - or shaking.
When asked what could have inflicted such serious injuries, Elstone later told police in an interview of an accident where the baby's 2-year-old brother had fallen on top of him when he was in a bouncy-net, and suggested that could perhaps have caused the injury.
However, medical experts refuted the claim saying the injuries were similar to that of a car accident or being dropped.
He was treated for a subdural haematoma - a serious condition where blood collects between the skull and the surface of the brain and had surgery as a result.
Crown prosecutor Steve Manning told the judge the boy was "happy and healthy" before entering Elstone's care in 2017.
"It was clear that from the defendant's point of view he was difficult to deal with," he said.
"On the morning of January 9, a healthy child was delivered into her care, but in the time calling 111 she believed he was crying, kept screaming and then the event occurs. She's shaken this child or used force in some way."
Manning referred back to the strong medical evidence from several experts throughout the trial.
"There is no medical or accidental cause which could impose these injuries."
He also referred to evidence that the Elstone found the baby "grizzly" and "difficult", sending text messages to a work colleague on the day of January 24 asking about other options for care.
Defence counsel Nicola Graham said that Elstone was an experienced caregiver who had looked after young children before.
"She had no problems asking for help and did so during the baby's care," she told Judge Rea.
She referred back to the first instance on January 9, saying that there was some uncertainty among medical experts about what may have occurred before emergency services were called - as his symptoms matched those of a seizure and no scans were undertaken at the time.
It was only after the incident on January 24 that experts discovered old blood on the baby's brain as well as new blood from the recent turn of events.
"I accept that it could have been a head injury and findings of old blood lead experts to believe that was the case - but it was not certain."
Graham also noted that there were no injuries such as bruising or damage to the neck.
"It would be an incredibly rare circumstance for a professional caregiver to shake a child and then take it back into her care."
Elstone has been remanded on bail until sentence on May 29.