They Shoot Horses Don't They?
Michael Sarrazin's character (the name eludes me) performs a "mercy killing" on Jane Fonda to put her out of her misery at life (hence the "flash-forwards" showing him on trial. The title refers to the fact that, when horses are in unbearable and incurable pain, such as when they break a leg, it's considered the humane thing to do shoot them and end their misery.
Thanks, enubrius!(Links open in new window)