Mr Smith, 29, of New Lambton, appeared in Newcastle Local Court via audio visual link from Cessnock Correctional Centre on Wednesday where he was committed for trial on charges of murder and an alternative charge of manslaughter.

The DPP had previously withdrawn a charge of reckless grievous bodily harm.

Mr Smith, who was represented by solicitor Keppie Waters, will appear in Sydney Supreme Court on July 17 where it is expected he will plead not guilty and get a trial date.

Emergency services were called to a home in Fairfield Avenue, New Lambton, about 4.30am on February 9, 2019, after the boy, who was allegedly in the care of Mr Smith, went into cardiac arrest. He died the next day.

Wednesday's committal was a significant development in a case that, due to its "exceptionally complex and highly sensitive" nature, had dragged through the local court in the 16 months since Mr Smith's arrest.

The charge certification process, whereby the prosecution determine the offences a defendant will face in a higher court, had taken more than a year to finalise - twice as long as is permitted.

The sticking point and crucial piece of evidence in the case is the autopsy report examining the boy's death and the Office of the Director of Public Prosecutions (DPP) had been forced to repeatedly apply to further extend the period of time for the prosecution to file a charge certificate while they waited for the report to be served.

The autopsy report was served in December, 2019, and the DPP asked for more time before finalising the charges in March.

The Newcastle Herald reported in March that the mother of the six-month-old boy - who had been behind bars charged with failing to provide for child causing danger of death, concealing a child abuse offence and doing an act intending to pervert the course of justice - had all charges relating to the boy's death dropped.

The mother, who cannot be identified, pleaded guilty to two counts of driving while disqualified and was sentenced to time served.