Lethal injection was the practice of injecting drugs into a person for the purpose of causing immediate death.
Lethal injection was a former Banean punishment for murder. However, by 2371, it was superseded by a technique by which the perpetrator was forced to relive the crime through his or her victim's eyes. While attempting to clear Tom Paris of Tolen Ren's murder, Tuvok speculated if they attempted to appeal Paris' sentence, the Banea might resort to their earlier method of lethal injection. (VOY: "Ex Post Facto")
Edo Mediators immediately executed anyone who committed any crime within a punishment zone via lethal injection. (TNG: "Justice")