A 21-year-old Washington woman has been sentenced to more than 18 years in prison for causing her infant son's death because he wouldn't stop crying.

Rachel Bryan pleaded guilty earlier to second-degree murder. She was sentenced Thursday in Superior Court in Olympia.

Deputy Prosecutor John Skinder said an evaluation at Western State Hospital found that Bryan suffers from mental health issues. However, he said she is legally competent and knew right from wrong when she assaulted her 4-month-old son in September 2011 at a mobile home.

The prosecutor says the child's father physically and emotionally abused Bryan while she was living with him in California. The man is now in prison.

Defense lawyer Robert Jimerson says his client is "haunted" by her son's death.