It took but a day for a three-year-old girl to die from the terrible injuries she suffered when a 100kg man stood on her stomach.

But it took her killer - gripped by fear, shame and guilt, seven months to admit to the extent of his crime - that he placed his full weight on the child "in frustration" after tripping over her as she played on the floor.

He then told the little girl to tell her mother she had a stomach ache and sent her to bed.

She died the next day from blunt force trauma to the abdomen, a ruptured liver and bleeding in both kidneys.

The 22-year-old man, whose name is suppressed, has pleaded guilty to child homicide over the death in 2015.

He placed his entire 100 kilograms of weight on the girl after he tripped over her, senior crown prosecutor Kerri Judd QC told the Victorian Supreme Court on Friday.

"In frustration, he turned her around and stepped on her stomach with one foot," Ms Judd told the plea hearing.

"He took his other foot off the ground, thereby putting his entire weight on her."

By noon the next day, she had become pale and limp and was declared dead in hospital soon after.

The accused did not admit to his crime for seven months, by which point the police investigation had intensified.

A psychologist who treated the man said his client did not come forward sooner because of his sense of guilt, and fear of the consequences he faced.

"Shame, guilt and fear had left him paralysed," psychologist Patrick Newton told the court.

The mother of the child wiped away tears and had to excuse herself numerous times from court as the graphic details of the crime were laid bare.

In her victim impact statement read to the court, the girl's mother spoke of her feelings of betrayal.

"I was lied to for seven months when he knew the truth," she said.

"I no longer trust anyone after being betrayed ... like this."

The girl's biological father said he suffered severe anxiety and had lost 44kg since his daughter's death.

Defence barrister Simon Moglia said his client's confession to police "demonstrates remorse, albeit after time".

The man is due to be sentenced by Judge Jane Dixon on February 24.