A 5-month-old baby killed by his mother suffered severe brain injures, bruising to his head and neck, and had meth in his system, a Perth court has heard.
Melissa Louise Bulloch, 27, has pleaded guilty to the manslaughter of her son Lachlan, who was found dead at his Hamilton Hill home in January 2014.
Prosecutor Carmel Barbagallo told the WA Supreme Court during a sentencing hearing on Thursday that Bulloch's abuse of the baby in the months leading up to his death included blowing cannabis smoke into his face, leaving him in a car, and shaking and swearing at him.
The court heard the Department for Child Protection was also involved with the family and police listened to Bulloch's phone calls and conversations after the baby's death.
On one occasion, she said: "I'm sorry Lachlan ... for killing you, my sweetheart. That freaked me out."