The American stepmother of Australian girl Zahra Baker has pleaded guilty to murdering the girl and hiding parts of her body.

Zahra was reported missing from her North Carolina home in October last year and parts of her dismembered body were found two weeks later.

Handcuffed and wearing a pink prison jumpsuit, Elisa Baker, 43, showed little emotion as she appeared in a North Carolina court overnight.

She will serve between 14 and 18 years in jail after doing a deal with prosecutors and pleading guilty to second-degree murder.

She also confessed to desecrating and hiding her step-daughter's body, and subjecting her to verbal, physical and psychological abuse.

Police say they found blood traces on the walls, floor and ceiling of Zahra's bedroom, and phone records put Baker at the dump site where the girl's remains were found.

Zahra was reported missing from her North Carolina home in October 2010. ( www.hickorygov.com )

Elisa Baker's Australian husband, Adam Baker, told the court he "hated" his wife.

"Lisa, I trusted you with the most precious person in my life," he said.

"Zahra loved you more than anything in the world. You took the life of the most wonderful and loving little girl."

Zahra’s biological mother Emily Dietrich read a statement to the court saying her daughter was "pulled apart like some human puzzle and discarded like rubbish for wildlife to graze on."

Zahra was born in Wagga Wagga in New South Wales and had twice survived cancer.

She moved to the US from Townsville in north Queensland with her father in 2008.

She had a prosthetic leg, which was found after her murder, and two hearing aids.

Not all her remains have been recovered, and the precise cause of death is still not known.