A Tasmanian man claims he broke his newborn baby's ribs because the infant kicked him in the testicles while he was changing his nappy.



"If he kicked you in the nuts, you'd go off your head too," he later said to police.



"When I get wild, I don't know my own strength."



Crown prosecutor Kate Brown yesterday told the Supreme Court in Launceston that 23-year-old Kenneth William Blake broke both the baby's legs, three of his ribs and caused bleeding to his eye and bruising to his cheek on different occasions in the six- week-old's life.



Blake yesterday pleaded guilty to ill-treating a child.



His 21-year-old partner, Khristy Maree Fisher, pleaded guilty to the same charge on the basis she knew what her boyfriend was doing - and had done - and failed to seek medical attention for her baby.



Ms Brown told Chief Justice Ewan Crawford the offences were committed at George Town on various occasions between February and March 2009.



The violence against the baby was only discovered when a child health nurse made a scheduled visit to the pair's home.



She was met at the door by Fisher, who told her she was worried about the baby's leg as it was swollen.



When told the baby needed urgent medical attention, Blake responded by saying he felt "like slitting some ----'s throat".



Fisher later told police they had not sought medical attention for the leg injury in particular because they "thought it was just a fracture".



It was.



The baby was taken to hospital by ambulance where he was given both morphine and codeine on top of paracetamol to alleviate the pain caused by his injuries.



Neither parent attended or contacted the hospital at any point during his stay.



His physical injuries have since healed.



Both the child and a sibling are no longer in the care of the parents.



Fisher is now 4 1/2 months' pregnant.



Chief Justice Crawford yesterday rejected Blake's version that the injuries were inflicted accidentally.



The judge said it was not possible for a six-week-old baby to kick anyone with enough force to hurt them.



He rejected Blake's story that the fractured ribs must have been caused by him strapping the baby into a pram too tightly.



He rejected the suggestion the facial injuries were caused by the baby falling forward while propped up in a sitting position.



Fisher clutched Blake's knee throughout yesterday's extended court proceedings, hanging her head as the judge remanded both her and Blake in custody to reappear for sentence on August 19.



The delay is because the lawyers for both prisoners want to obtain psychiatric assessments of their clients before sentencing.



Chief Justice Crawford has also ordered a disputed facts hearing be held in the meantime - at a date to be confirmed - due to the difference between Blake's claims the injuries were inflicted accidentally and the Crown's assertion they were the result of deliberate acts of violence against the baby.

-The Tasmanian Examiner