The 45-year-old woman who cannot be named due to a court order, hugged her family as she was escorted into custody on Tuesday afternoon.

The 20-month old boy was found unresponsive at a property outside Dubbo in NSW's Central West, by paramedics on March 23, 2015, after the foster mother called triple-0.

The court heard the woman was unaware paramedics had answered the call when she was heard saying "they're going to think I bashed him", before asking "am I going to get in trouble for this?" when she called triple zero for help at 5.17am.

Despite multiple attempts to revive the child, he was pronounced dead at 7.30am at Coolah District Hospital.

The court heard investigations found the boy had injuries to his bottom area and extensive bruising to his abdomen and face.

It was also revealed he had suffered a stomach rupture and a broken femur - the break so severe, it was compared to that sustained in a car crash.

The child also was found with vomit in his mouth and on sheets.

The foster mother, who has three biological children of her own had given multiple, varying accounts to police of what happened on the night of the child's death.

In January 2018 the woman was arrested in Geurie and charged with murder.

The former foster mother pleaded not guilty to one count of murder and has spent almost four years on remand.

A two and a half week judge-alone Supreme Court trial began in Dubbo last month before Justice Richard Cavanagh who handed down his judgement on Tuesday.

Justice Cavanagh said while he didn't know what precisely what occurred in the hours before the child died, he found all three injuries occurred in the woman's home that night.

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Ultimately he was satisfied the foster carer "assaulted or attacked" the infant which led to his injuries.

"I'm satisfied when the child came home that night he was not suffering from the type of bruising on his face or some of the other bruising [on his stomach]," Justice Cavanagh said.

"He was not suffering from a fractured femur. He was not suffering from the effects of stomach perforation. He had sustained those injuries some time from coming home and death."

The woman told police she had consumed five to six beers that night, and the court heard one of her children had given evidence they saw her mother forcing the toddler into the bath and yelling.

"Whether she was somewhat affected by alcohol is irrelevant," Justice Cavanagh said.

"The force applied to cause the injuries would have been significant. The femur and stomach injuries could not have been caused by some accidental excessive gripping or inadvertent twisting.

"Whether or not the actions of the accused were only a temporary loss of control, such acts by an adult on a 20-month-old toddler could only have been intended to cause grievous bodily harm."

The woman was taken into custody and a she will face a sentence hearing sometime in May.