The first opening narrative used from 1990 to 1995 featured the iconic sound of a police siren fading in, then out, followed by a male voiceover saying:
"In the criminal justice system, the people are represented by two separate yet equally important groups: the police who investigate crime and the district attorneys who prosecute the offenders. These are their stories."
The second opening narrative, used from 1995 to 2010, replaced the voiceover with a dramatic orchestral score and a montage of scenes from the show. The opening scene, depicting a crime in progress, was always the same, but the remaining scenes would change each episode to reflect the episode's theme.
It is noteworthy that while the opening narrative changed, the show's overarching theme remained the same: exploring the complex world of crime and the justice system.