Summary

• CSI franchise set the blueprint for shared universes with crossover episodes between four different shows, captivating millions of viewers.
• Each CSI spinoff, including CSI: Miami and CSI: NY, was introduced through backdoor pilot episodes within the original CSI series.
• The "CSI Trilogy" crossover event in 2009 brought together characters from all three original shows, proving the franchise's enduring popularity.

Shared universes may have become the norm for popular franchises, but the CSI crossover episodes were common in the shows before so many movies were doing it. The CSI franchise started in 2000 with CSI: Crime Scene Investigation, a show that later would also be known as CSI: Las Vegas. The story about a team of forensic scientists working to solve the strangest cases in Las Vegas was simple but interesting enough to create a thrilling show that would air for 15 years and see three spinoffs and a revival, CSI: Vegas.

The first CSI spinoff was CSI: Miami, a show that started in 2002 and ran for 10 seasons. Two years later, CSI: NY, debuted on CBS and a fourth spinoff arrived in 2015 with CSI: Cyber, a few months before the end of CSI: Crime Scene Investigation’s original run. For each of the CSI spinoffs, the introduction of the characters and the premise of the show debuted in backdoor pilot episodes. Now, crossovers between at least two CSI teams have become common. There are plenty of CSI crossover episodes, including ones that served as backdoor pilots.

"Cross Jurisdiction"

CSI: Crime Scene Investigation, Season 4, Episode 22

The story of Horatio Caine and the CSI: Miami crew started in CSI: Crime Scene Investigation season 4, episode 22, “Cross Jurisdiction.” Cross Jurisdiction, which aired on March 9, 2002, starts as a regular CSI: Crime Scene Investigation episode, with the Las Vegas forensics team members Grissom and Catherine being called to a crime scene after LVPD Chief Duke Rittle is found dead at his home.

Rittle had a wife, who later in the episode is also found dead, and a daughter, Sasha, who had been missing since the investigation started. When the crew of Las Vegas receives the information that a girl matching the description has been seen in Miami, Catherine and Warrick are sent to Florida, and audiences are then introduced to Detective Horatio Craine and the CSI from Miami. The episode worked great to introduce the new characters and earned over 27 million viewers - only one other episode of the season garnered more live viewers.

"MIA/NYC NonStop"

CSI: Miami, Season 2, Episode 23

CSI: Miami season 2, episode 23, “MIA/NYC NonStop,” was the backdoor pilot for CSI: NY. The episode aired on May 17, 2004, and introduced audiences to Mac Taylor, head of the CSI New York, as well as to Stella Bonasera, Aiden Burn, Dany Messer, and Sheldon Hawkes – all of who would be key characters in CSI: NY. After promising Laura, a young girl whose parents were killed, that he was going to find the murderer, Horatio Caine heads to New York while following a lead on a potential suspect.

However, by the time he arrived, the suspect had also been killed, and now the CSI: Miami detective had to work with the CSI from New York to better understand what had happened. Like the first CSI backdoor pilot, the episode garnered a lot of interest, this time earning 2 million more live viewers than any other episode of the season, showing that there was a lot of interest in CSI: NY.

"Felony Flight"

CSI: Miami, Season 4, Episode 7

With both CSI: Miami and CSI: NY already established, all sorts of CSI crossovers were now possible. CSI: Miami season 4, episode 7, “Felony Flight,” was the first of a two-episode crossover with CSI: NY. It aired on November 7, 2005, and it saw Mac Taylor from the NYPD going to Florida to help CSI: Miami's Horatio Cain and his team catch a serial killer on the run.

However, the chase for Henry Darius was more challenging than they could have anticipated, and the episode ended with the serial killer still on the run and heading back to New York.

"Manhattan Manhunt"

CSI: NY, Season 2, Episode 7

The chase for Henry Darius continued in CSI: NY season 2, episode 7, “Manhattan” Manhunt,” which aired on November 9, 2005. The serial killer was now back in New York, leading to Mac and Horatio regrouping in Manhattan. The episode is mostly centered on the New York crew, and Horatio is the only character from Miami to appear. This particular crossover might not have been as satisfying as the previous crossovers since only one character traveled back and forth, but fans still weren't losing interest in them.

Without A Trace/CSI Crossover

Without A Trace, Season 6, Episode 6/CSI: Crime Scene Investigation, Season 8, Episode 6

On top of the usual CSI crossovers, 2007 saw a special team-up between the also procedural drama series Without a Trace and CSI: Crime Scene Investigation. The crossover happened in two episodes, Without a Trace’s “Where & Why” and CSI: Crime Scene Investigation’s "Who & What.”

The story followed Without a Trace’s Jack Malone teaming with the CSI crew of Las Vegas when a missing person case turns into a murder investigation. The crossover saw a ratings increase for both episodes, proving that there was plenty of interest in crossovers even with outside series. Without A Trace's audience increased so much that the episode had more viewers than the show had in the previous year.

CSI: Trilogy

CSI: Miami, Season 8, Episode 6/CSI: NY Season 6, Episode 7/ CSI: Crime Scene Investigation, Season 10, Episode 7

While there had already been CSI crossovers in pairs, it was only in 2009 that all three CSI shows came together for one big crossover event. The “CSI: Trilogy,” as it is called, started with CSI: Miami season 8, episode 7, “Bone Voyage.” The second part was in CSI: NY season 6, episode 7, “Hammer Down.” Last, the “CSI: Trilogy” crossover event was concluded in CSI: Crime Scene Investigation season 10, episode 7, “Lost Girls.”

During that time, it was Ray Langston, played by Laurence Fishburne (The Matrix), who was leading the Las Vegas crew. “CSI Trilogy” was the only crossover between all three original CSI shows, and it followed a massive investigation of a criminal organization that had been acting all over the country.

While all the episodes boasted over 14 million viewers each, it was clear that Las Vegas was still the show that most CSI fans flocked to as the final chapter of the trilogy had three million more viewers than the first two episodes. The downside to a crossover like this one is that fans didn't get to see multiple characters from different series interact. Instead, only one character appeared in all three episodes - Ray Langston. Not allowing more character interactions is a missed opportunity for the CSI crossover episodes.

"In Vino Veritas"

CSI: Crime Scene Investigation, Season 13, Episode 13

The two-shows-only crossovers would return in 2013, with CSI: Crime Scene Investigation season 13, episode 13, “In Vino Veritas.” Mac Taylor was heading to Las Vegas to spend time with his girlfriend, only to find out that she was missing. The CSI: NY character then has to team up with his friend D.B. Russell, who had become the head of the Las Vegas crew after Laurence Fishburne exited the show in 2011. Fishburne would go back to star in theatrical movies like Man of Steel and Batman v Superman.

"Seth And Apep"

CSI: NY, Season 9, Episode 15

Russel and Taylor were not able to find Taylor’s girlfriend, Christine, in “In Vino Veritas.” That led to CSI: NY season 9, episode 15, “Seth and Apep.” The duo did find out who had kidnapped Christine, but the criminal known as Jimmy Bond wanted to use her as a bargaining chip in exchange for the stolen diamonds he had lost. However, it was revealed in “In Vino Veritas” that Christine had been kept in New York the whole time, leading to Taylor going back to Manhattan, now with the company of CSI's Russell (played by Ted Danson).

"Kitty"

CSI: Crime Scene Investigation, Season 14, Episode 21

More than 14 years after the premiere of CSI: Crime Scene Investigation, a fourth CSI show, CSI: Cyber, began development. As it happened with CSI: Miami and CSI: NY, the audiences’ introductions to the main character and premise of CSI: Cyber came in the form of a backdoor pilot. CSI: Crime Scene Investigation season 14, episode 21, “Kitty,” featured Patricia Arquette as a guest star, and it saw her character Avery Ryan helping CSI Las Vegas solve the murder of a casino owner's wife. The CSI crossover episode aired in 2014, and CSI: Cyber season 1 premiered a year later.

By the time this CSI episode aired, live viewers weren't in as high of a number as the early seasons of the show. The episode had nearly 10 million viewers in the United States, but it was simulcast in 171 countries when it aired, breaking a world record. It made good use of its characters and proved that the CSI franchise had real staying power.