When “NCIS” premiered few viewers knew that NCIS — Naval Criminal Investigative Service — actually existed, or that unlike other military investigative agencies, more than 90% of its staff is civilian.

Producers knew NCIS is real and not only did they consult with military advisers, but they also hired a retired NCIS agent as the series’ technical adviser.

“We couldn’t do this show without the assistance of consultants like former NCIS agent Leon Carroll Jr. and our friends at the U.S. Navy and Department of Defense,” says showrunner Gary Glasberg. “Our goal is to be as authentic as possible, and having them on board helps make that happen.”

The technical adviser since season one, Carroll, who worked everything from general crimes to foreign counterintelligence during his 23 years at NCIS, is the show’s secret weapon in bringing authenticity to the screen.

“I spent my first season explaining to the cast and crew that there really was an NCIS,” Carroll says. “I think they started to believe it after I started bringing in agents and other employees from the real agency to visit the set.”

The bulk of Carroll’s work involves consulting on scripts to ensure plots and dialogue are plausible. He’s also on set for scenes involving crime scene investigations, raids, and arrests to coach actors on proper protocol and procedures.

“Today I provide more assistance to guest actors playing law enforcement officials or agents than I do with our regular cast. They all have it down now,” he says.

A recent script mentioned paychecks. Carroll pointed out that the government uses direct deposit, but explained how employees get Leave and Earnings Statements detailing their pay, withholding taxes, donations and leave time. That fact added authenticity to the story.

While Carroll admits to some creative license on the show — NCIS doesn’t have its own medical examiners and the DOD consolidated all military labs into a single facility — he says he gets consistently positive feedback from past and present NCIS agents.

“What they love more than the entertainment value of the show is that it put the agency on the map,” Carroll says. “They always tell me, ‘We no longer have to explain who we are.'”

‘NCIS’ 200th Episode
Dramatic growth spurt | Showrunner transition goes smoothly | Authenticity matters | Procedural also a cable, worldwide sensation