A Nova Scotia judge says he wants another assessment done on a foster mother who admitted to abusing a little girl in her care, before he makes a decision about her sentence.

Susan MacDonnell of Dartmouth was supposed to be sentenced this morning, after she pleaded guilty to aggravated assault and failing to provide the necessities of life.

MacDonnell was charged after a toddler in her care was treated at the IWK Children's Hospital in Halifax for malnourishment in 2010.

MacDonnell has fostered nearly 30 children over 13 years and has no previous record.

Today the judge said he has never felt as challenged as he does with this case.

"Justice Coady was left with concern that he doesn't understand why something like this could happen, why someone like Ms. MacDonnell, a foster and adoptive parent, would essentially almost kill her child," Crown Attorney Catherine Cogswell told CTV News. "So, he's ordered a full-blown psychiatric assessment to assist him in giving a proper decision."

The Crown is asking for five years in jail, while the defence is asking for two.

MacDonnell will be back in court next month to set a new date for sentencing.