A drug addict who fatally dropped a six-month-old baby on its head has been jailed in NSW for four years and nine months.
Newcastle Supreme Court Justice Helen Wilson says both Jie Smith and the baby's mother repeatedly lied about what happened in the lead-up to the child's death and she could not say who was to blame.
The judge said she had to sentence Smith on the basis he failed to get medical help in time to save the baby, who suffered serious head injuries, not for causing the boy's death.
Smith, 31, was charged with murder after being alone with the baby for two-to-three hours at New Lambton in suburban Newcastle when the child suffered a fractured skull.
However, Smith was found not guilty of murder but guilty of the lesser charge of manslaughter.
He told the jury during a two-week trial in July that the boy's mother had repeatedly punched and shaken her son about 2am on February 9, 2019, before leaving the baby with him after she had been given her share of the drug ice he had bought earlier.
Smith claimed he was holding the distressed boy when the baby likely suffered a seizure from the earlier attack and slipped from his arms, causing him to hit his head on the ground.
The mother denied assaulting her son and claimed he was unharmed when she left.
Justice Wilson on Wednesday said "considerable uncertainty" remained about the events leading up to the baby's death.
The judge said the truth of what happened or who was to blame could not be established because the conflicting evidence from Smith and the mother was unreliable.
"What can be said is that in his tragically brief life, (the baby) was exposed to danger and danger found him," the judge said when jailing Smith for four years and nine months, with a minimum of three years and six months.
"How and in whom that danger manifested is not established on the evidence."
Justice Wilson said she could not accept the evidence from both Smith, who had been placed on a two-year community corrections order for assaulting his pregnant girlfriend four months before the baby's death, and the mother because they were both lying.
The judge said police had not yet made a decision about charging the mother over the child's death, but it was unlikely.
"It is acknowledged there must be a real sense of injustice or at least a justice not fully done because the court cannot truly vindicate (the baby's) death," Justice Wilson said.
"It is another of the features of this case which will no doubt cause distress to those most involved and which should distress us all as a community.
"That a child can die violently at the hands of someone who should have cared for him and yet the community be ignorant as to the circumstances of the violence is shameful for us all."
The judge said Smith failed the baby "in the most grievous way", knowing he was injured but failing to get help "until it was too late".
Justice Wilson rejected Smith's claims he initially lied to police about what happened to protect the mother despite the fact they were only in a casual relationship based on drugs and sex.
The baby's mother, who has four other children, previously told the court she was not the best mum but would never hurt her children.
"I feel numb. (The baby) didn't deserve this," the mother said.
"He was a happy little boy. I still struggle to understand what has happened."
