Aftershock

Every episode of Law & Order opens with the investigation of a crime, usually a murder. This is the only episode that does not open with a crime or feature a criminal investigation and prosecution. This episode opens with four of the main characters witnessing the lethal injection of a prisoner--a convicted murderer--and it revolves around the characters' reactions to the execution.

Though this was arguably one of the most powerful entries in the series, the entire premise is fictitious. No one has been executed by the state of New York since 1963.