Martin "Marty" Deeks is a Detective with the Los Angeles Police Department and who serves as a liaison to NCIS via the LAPD.
As such, Deeks is responsible for facilitating communications between both agencies, and coordinating joint operations involving LAPD components.
In recent years, Kensi and Deeks have begun dating.
The son of a man named Gordon John Brandel and an unnamed woman, Deeks was born on January 8th, 1979 in California but Deeks didn't have a happy childhood as his father was an alcoholic who frequently abused Deeks and Deeks's unnamed mother.
One day, Brandel became so drunk that he started wielding a shotgun at Deeks and his mother.
In response, young Deeks shot Brandel non-fatally with Brandal later ending up in prison.
Deeks later presumably moved away and attended college before choosing to join the Los Angeles Police Department.
NCIS: Los Angeles Season 1
Deeks first appeared in the episode, "Hand to Hand", undercover as a mixed martial artist named "Jason Wyler". He managed to get into a local gymnasium that served as front for a drug smuggling operation. The Office of Special Projects targeted the gym after Daniel Zuna, a Marine on leave was found murdered in an alleyway outside the nightclub.
NCIS Special Agent Sam Hanna went in undercover, using the alias, "DeMarco Williams" with Sam fighting Deeks and knocking him out.
During a subsequent encounter, both of them were taken into custody to preserve their covers. It was only after being released from the holding cells that he was revealed to be a Detective with the LAPD. Detective Deeks saved Agent Hanna's life after his cover was blown.
Deeks was later seen in a bar, drinking away his sorrows with a cup of coffee while still smarting from the tongue-lashing he had received from his boss.
Hetty later arrived at the same place and, after revealing that she too had suffered the same treatment from her boss, told Deeks that she had decided to create a liaison position between the LAPD and NCIS.
Deeks was in disbelief at first but upon Hetty offering him the position, having told Deeks that he was the suitable candidate for the job, Deeks accepted.
Deeks joined the team in "Fame" to help them solve a case before leaving NCIS to go take part in a deep undercover operation despite the fact that some of the team, including Sam were hostile to him given that Deeks's predecessor, Agent Dominic Vail who was still missing had not returned to the team.
During a mission to save Kensi, with Hassad Al-Jahiri weakened by a gunshot from Callen, Deeks took the opportunity to finish Hassad by dropping to the ground and then firing a single shot which killed Hassad instantly.
Deeks then left the team to go on a deep undercover mission and was only mentioned once in the Season 1 episode, "Burned".
NCIS: Los Angeles Season 2
In the Season 2 premiere episode, "Human Traffic" after his undercover mission went south, Deeks contacted Hetty for help and begged for her to assist in his mission which involved underage young girls.
He officially became Kensi's partner and deceased Agent Dominic Vail's replacement in the next episode, "Black Widow", resulting in him joining the team permanently albeit as a liaison officer.
NCIS: Los Angeles Season 3
In "The Debt", Deeks's position was terminated and he was fired from NCIS after unintentionally shooting an unarmed man. It was later revealed that the supposedly dead victim was actually an undercover NCIS Agent working out of Washington D.C.
The incident gave the LAPD a reason to take Deeks back after so long while also cutting their ties with NCIS. The OSP team were eventually able to find out the identity of the mole and in the end, Deeks returned to the OSP, having been reappointed as the LAPD/NCIS Liaison Officer.
NCIS: Los Angeles Season 4
NCIS: Los Angeles Season 5
NCIS: Los Angeles Season 6
Hand to Hand Combat
Callen and Deeks share a friendly relationship at work. However, Callen often joins Sam in teasing Deeks; mostly about his hair, his partnership with Kensi and his dog, Monty.
Callen does show genuine concern for his co-worker when Deeks gets shot in the second season episode "Personal".
At first, Sam was somewhat hostile towards Deeks, calling him 'temp' and being unhappy when Hetty placed him in Dom's seat. However, he soon warmed up to Deeks and spends most of his time teasing him with Callen. When Deeks gets shot, Sam assists him in altering his daily routine. There is still friction between Deeks and Sam throughout season 3 and 4, usually it is kept at bay since they are not partners.
However, in the final episode of season 4, Deeks and Sam work together. Deeks confronts Sam and Sam admits that he feels Deeks has some flaws in his character.
Later in the episode, Deeks saves Sams life and both he and Sam are captured and tortured at the end of the season 4. He can be seen visibly pained and distressed while being forced to watch Deeks being tortured. In the season 5 premiere, after Granger and Kensi find the two, Sam asks Deeks if he gave up Michelle, to which he replies that he didn't. Sam goes to Deeks' hospital room later on and states that he owes Deeks for the rest of his life. Deeks confides in Sam that he was thinking about quitting as a cop, to which Sam says would be a bad idea, admitting that Deeks is an excellent cop.
Deeks and Kensi share a complicated partnership due to the fact that Kensi is the more experienced of the two and also because Deeks permanently replaced Kensi's deceased partner. Despite this they do care for each other, although they get on each other's nerves at times. There have even been hints that Deeks and Kensi are romantically interested in one another, and there has been constant continuous moments during which they have flirted with each other and have come close to have romantic contact, although they both strongly deny it. Despite this, they share a kiss in the season 4 finale. In season 5, Deeks admits to Kensi that she was the one person he thought of through his torture after being captured, thus saving his life by keeping him going. This detail leaves her clearly emotional.
The two resume their usual friendship after a bit, until Deeks takes her out on a date without actually telling her it was a date. Kensi says he is back to his original problem with poor communication skills and tells him to say something that he actually means, because if they can't communicate then things won't work between them. Deeks finally tells her that he didn't want to be there with her. Kensi appears confused before he says that he wants to be with her at his place right now. Kensi stares at him for a moment, clearly thinking about what to do, before she gets up and walks away from the table as Deeks takes a breath before following after her. In the next episode, Frozen Lake, it is implied that Deeks and Kensi spent the night together when Deeks is at work early on and won't make eye contact with anyone and Sam notices as Kensi walks in that she is wearing the same outfit she had on the day before, leaving her flustered. When they get called for a mission, Sam and Callen watch as Deeks and Kensi awkwardly walk out of the room, unable to look each in the eye. In the most recent episodes Kensi and Deeks play it off trying to get things back to normal before all of the feelings and Kensi going to Afghanistan. Upon her return, though, there is still a little bit of tension between the two.
- Originally used a Glock 17 before switching to Beretta 92FS. In Season 3, Deeks switches to a Smith & Wesson 5944 instead which he has continued to use to this day.
- Much like his counterpart, Anthony DiNozzo in the original "NCIS" series, Deeks had a horrible childhood and as such, uses humor and he also tends to be the comic relief of the group, but can be serious when needed and also just like Ziva David, Deeks is also the third partner that Kensi has had much like Tony who had two partners: Agents Vivian Blackadder and Caitlin Todd before Ziva joined him.
- Despite the stress of his job, Deeks is shown to be deathly afraid of needles as revealed in Episode:Touch of Death. He can be heard screaming before passing out when being forced to take a vaccine although he insists that he tripped.