ORANGE CITY, Iowa (AP) — A northwest Iowa man accused of stabbing to death his 84-year-old grandfather plans to use a defense of diminished capacity. The attorney for 20-year-old Santos Rodriguez Jr. filed the notice Tuesday in Sioux County District Court. Rodriguez has pleaded not guilty to charges of first-degree murder and arson. He’s accused of stabbing Luis Luevanos in his Rock Valley home on Oct. 29 and setting the man’s house on fire.

Police say Rodriguez was later arrested in Utah. Iowa investigators say Rodriguez admitted during a police interview to stabbing his grandfather and setting the fire. Rodriguez’s trial is scheduled to begin Sept. 18 in an Orange City courtroom.