A young Northern California mother who was believed to be suffering from depression when authorities say she stabbed her infant son to death has pleaded not guilty to a murder charge.

The Oakland Tribune reports (http://bit.ly/1srAIvh ) that 23-year-old Ashley Renee Newton of San Jose entered the plea on Thursday.

Authorities say Newton ran up to officers at a park in Livermore in April with the lifeless body of her son, William Sherman, in her arms. She allegedly acknowledged having killed the 7-month-old boy, who had been stabbed with a pocket knife.

Authorities have said Newton had a history of depression and appeared to have self-inflicted knife wounds on her wrist.