Keeping the Law & Order franchise is confusing, unless you're a fan who's been following it since network-of-origin NBC debuted the Dick Wolf produced series in 1990. The original L&O series ended in 2010, after 20 years. Its opening narration has reached iconic status: "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." Subsequent spin-offs used variations of the original opening narration.
Law & Order basically defined the procedural drama for today's television audience and followed the same format for pretty much its entire run: The show opens with the crime and police investigation and is followed by the Manhattan Disctrict Attorney's prosecution.
The series' was unique in that there was minimal focus on the lead detectives and D.A.s personal lives, and concentrated on the actual crime. Within the franchise and other Wolf productions there has been, and continues to be, quite a bit of "crossover."
Law & Order – premiered the fall of 1990 and was cancelled by NBC in May of 2010. It was notable for its revolving cast of both detectives and D.A.s. L&O's first detectives were George Dzundza and Chris Noth, Dan Florek as the Captain, and Michael Moriarty as the Executive Assistant DA. Various actors rotated into the roles before Jerry Orbach and Jesse L. Martin as the detectives, S. Epatha Merkerson as the captain and Sam Waterston as the DA held the positions steady for several years. (Florek had moved to another branch of the franchise.) When the series ended, Jeremy Sisto and Anthony Anderson were the detectives. Wolf attempted to find a cable net to take the series and also considered a telefilm to conclude it, but neither panned out.
Law & Order: Special Victims Unit/SVU (1999 to present): This first spin-off focuses primarily on the detectives of SVU which investigates sexually-based offenses. Wolf ‘s acclaimed, but short-lived "Homicide" series featured quirky Det. Munch and star Richard Belzer joined SVU with his partner, Fin (Ice-T). But the series' stars are Mariska Hargitay as Benson and Christopher Meloni as Stabler.
Law & Order: Criminal Intent (2001 to present): This series introduced Det. Robert Goren (Vincent D'Onofrio), brilliant, observant, methodical and prickly, and his forthright no-nonsense partner, Eames, played by Kathryn Erbe. This show focuses on the high-profile (aka "Major Case") cases. It currently airs on USA, a cable net owned by NBC/Universal., but debuted on NBC The series ends with its tenth season, in 2011.
Law & Order: Trial by Jury (2005-2006): Orbach took his tough Lennie Briscoe to this series, which focused on the legal preparation by both sides. Orbach's death (while the series was actually filming) and the tough competition from CBS' Numb3rs garnered it low ratings and it was canceled, after only a season.
Law & Order: Los Angeles (2010 to present): The latest installment in the franchise stars Skeet Ulrich, is shot and set in Los Angeles, the first of Wolf's L&O series to not be shot in New York City. It was met with mixed reviews.
Other related series include Law & Order UK, the aforementioned Homicide, New York Undercover, Crime & Punishment, Deadline and Conviction.