A University of Pittsburgh researcher charged in the cyanide poisoning death of his wife last year has been convicted of first-degree murder.

Jurors say they found 66-year-old Dr. Robert Ferrante's explanations unbelievable, and they were moved by a recording of a 911 call he made while his wife was groaning, moaning and gasping for air in the background.

Friday's verdict means faces a mandatory sentence of life in prison in the April 2013 death of 41-year-old neurologist Dr. Autumn Klein.

The jury agreed with prosecutors who accused Ferrante of lacing his wife's energy drink with cyanide. Authorities say he bought the poison with a university-issued credit card.

Ferrante denied poisoning his wife. He said the cyanide he bought was for stem cell experiments he was conducting on Lou Gehrig's disease.