The oldest daughter of a Utah doctor accused of killing his ex-wife says her father asked if he was a monster after her mother's death.

Nineteen-year-old Malkie Wall testified Thursday that John Brickman Wall had a mental breakdown and asked whether he was responsible for the death of her mother, cancer researcher Uta von Schwedler.

Lawyer Fred Metos has said aggressive police questioning caused the breakdown. John Wall was treated at a psychiatric facility shortly after.

Von Schwedler was found dead at her Salt Lake City home in 2011. Prosecutors allege her 51-year-old ex-husband killed her during a custody battle, but defense attorneys say she could have killed herself.

Von Schwedler drowned with a fatal dose of anti-anxiety medication in her system. A medical examiner stopped short of ruling whether her death was a homicide or a suicide.