American serial killer John Wayne Gacy was executed by lethal injection for the murders of twelve teenage boys and young men in a series of killings committed between 1972 and 1978.

John Wayne Gacy was an American serial killer and sex offender who raped, tortured and murdered at least thirty-three young men and boys between 1972 and 1978 in Norwood Park Township, Illinois, a suburb of Chicago. He became known as the "Killer Clown" due to his public performances as a clown prior to the discovery of his crimes.

Lethal injection is the practice of injecting one or more drugs into a person for the express purpose of causing death. The main application for this procedure is capital punishment, but the term may also be applied in a broader sense to include euthanasia and other forms of suicide. The drugs cause the person to become unconscious, stop their breathing, and cause a heart arrhythmia, in that order.