Harris died Sunday at an assisted-living center in New Haven, Conn., son James told The New York Times.
Harris was convicted of second-degree murder for the March 1980 shooting death of Dr. Herman Tarnower, a 69-year-old cardiologist who wrote the bestseller "The Complete Scarsdale Medical Diet" with whom she had a 14-year relationship, in his Purchase, N.Y., home.
Harris, a 56-year-old divorced mother of two, was sentenced to 15 years to life in prison. She served 12 years at the Bedford Hills Correctional Facility where she helped teach other female prisoners child-rearing skills and established a center so babies born to inmates could be near their mothers. After her release, she created a foundation that raised millions of dollars for scholarships for children of women in New York state prisons.
What drove her to kill him, authorities said, was his dalliance with his office assistant, Lynne Tryforos, a 37-year-old divorced woman.
Harris testified at her trial that she bought a pistol with the intention of killing herself at his estate. She said he tried to stop her when she pulled the gun from her purse and it fired, striking him. She said the gun went off a second time while they struggled, but she couldn't account for the other two bullets that struck him.
The jury found her guilty.