"The eight year old child [suffered a] prolonged period of physical and emotional abuse for 12 months," he told the court.
"The defendant has made admissions that she caused the death of the child by assaulting her over a long period."
Mr Soper told the court forensic and pathology tests were being carried out, and the mother could face murder charges within a week once the results were available.
A midwife told police the mother could have been suffering from post-natal depression during the period of abuse, he said.
Leaso withdrew her child from primary school to allegedly hide the pattern of abuse, he told the court.
"In November 2010 the defendant removed her child from school following an intervention by the Department of Child Safety, it is alleged to conceal the child's injuries by taking her out of school," he said.
Leaso moved to Australia in 2005 and is now an Australian permanent resident.
Samoan community church members reportedly appeared in court in support of the mother, while a shocked outpouring of grief appeared on the Queensland Police's Facebook page.
Hundreds of comments were posted below news of the death, with one labelling the passing "sickening".
Chere Chapman said: "R.I.P innocent angel. My thoughts and prayers go to whoever loved her, gosh I hope at least someone showed her what love is sometime in her short little life."
Another comment said: "That is so sad just before Xmas ... Fly with the angels little one."
A 22-year-old man is due to appear in court on December 15 to face one charge of child cruelty after the girl's death, police said.
