Written by series writer Ken Sanzel, "Trust Metric" is set five weeks after the events in "The Janus List".
In "Trust Metric"'s story, a Federal Bureau of Investigation (FBI) team attempts to find a pair of double agents, one of them a former teammate, who have escaped from prison.
The episode also marks the television directorial debut of series executive producer and filmmaker Tony Scott.
[1] FBI Special Agent Megan Reeves (Diane Farr) and her boyfriend, Dr. Larry Fleinhardt (Peter MacNicol), have been spending time at a Buddhist monastery.
Worrying their father Alan Eppes (Judd Hirsch), Charlie's brother, FBI Special Agent Don Eppes (Rob Morrow), spends the five weeks reviewing the tape of former FBI Special Agent Colby Granger (Dylan Bruno), who is currently serving time in prison on charges of espionage.
There, they find Mason Lancer (Val Kilmer), a United States attorney whose birth in Beijing, China, to American parents led him to spy for the Chinese.
Tony Scott wanted to direct "The Janus List" but felt that he could not do so properly due to his schedule.
[3] Specifically, Scott wanted to change the show's momentum and pace instead of maintaining the status quo.
[5] To capture more natural character moments, Scott refused to hold rehearsals and began filming as soon as the actors came on set.
[7] At one point, he removed the wall and ceiling of the interrogation room's set to capture a specific camera angle.
Prior to Scott's arrival, series producers sent him a reel showing the actors' hair styles from the previous three seasons.
[9] The crew filmed a short arrest scene at the beginning of the episode at a real-life pool hall in North Hollywood.
[3] After obtaining approval from the California Highway Patrol and Caltrans, the crew filmed the ambush scene under I-10.
Val Kilmer, who worked with director Tony Scott in Top Gun, was cast as US Attorney Mason Lancer.
Continuing a trend that he had started in several of his previous films, Scott brought in several members of a real-life Vietnamese gang.
He felt that the gang members' appearance and their real-life experiences added an authenticity that could not be replicated through makeup and acting.
[4] Numb3rs series aerial cameraman David Nowell was called in to play the FBI surveillance pilot as well as to film the episode.
[12] At the time, the only actor to know about the story arc's resolution was Dylan Bruno, whom producers informed during discussions about "The Janus List".
[5] Jeffrey Robinson, a reviewer for DVD Talk, included "Trust Metric" in his list of highlighted episodes.
[16] Donald Liebenson, one of Amazon.com's editors, called "Trust Metric" "explosive" and "a Very Special Episode, complete with blazing action set pieces and even a Big Name Star (Val Kilmer!)
[17] On the Numb3rs season four DVDs, the bonus feature "Crunching NUMB3RS: Trust Metric" addresses the production of the episode.