Kellie Johnson

Kellie Johnson is charged with first-degree murder in the death of her young son. (Facebook)

A Saskatoon woman who is charged with first-degree murder in the death of her young son will undergo a psychiatric assessment.

Kellie Johnson appeared in a Saskatoon court room today and will stay in custody at least until her next court appearance in February.

On Saturday, Johnson's five-year-old boy, Jonathan Vetter, was found dead in a home in the 400 block of Avenue R South.

Police said he was suffering from a fatal injury, and while they know the cause of death no details have been released.

Police said the 35-year-old Johnson has a history of mental illness. Last year, she was the subject of a missing person report after she left a mental health facility.