|Martin A. (Marty) Deeks|
|Portrayed by||Eric Christian Olsen|
|Occupation||LAPD Senior Detective / Former Lawyer|
|Title||LAPD-NCIS Liaison Officer|
|Family||Father: Gordon John Brandel (deceased)
Marty Deeks (portrayed by Eric Christian Olsen) is a member of the Los Angeles Police Department who has been to law school and passed the California State Bar Examination. He accepts the position of NCIS/LAPD Liaison Officer at the end of the episode "Hand-to-Hand", in which he co-operated with the team when their investigation overlapped with his undercover operation. However, his position as Liaison Officer is not always effective given his less-than-friendly relationship with other LAPD officers, getting brushed off on multiple occasions and stating in the episode "Fame": "you know how it is with undercover cops. I've pissed off more than my fair share of shields".
At the end of his second appearance, "Fame", he tells Kensi that he will be going on a long-term undercover assignment and Kensi seemed disappointed by this. In the same episode, it is revealed through conversations between Hetty and Callen that they do not actually need a liaison officer, but that Hetty has been watching Deeks for some time and her true intention is for him to eventually become an NCIS agent. This is eventually revealed to him in the season two episode "Imposters" when Hetty presents him with a set of completed and signed NCIS application forms. In the same episode it is revealed that Marty's given name is Martin A. and that he was born January 8, 1979.
He appears as a series regular during season 2, during which time he reveals that he has never lived more than two miles away from the home where he grew up. He is also revealed to be a lawyer in the season premiere. He is partnered with Kensi Blye and frequently flirts with her, although he is not above attempting to use her as a wingman to meet other women. Deeks has a comic book collection.
When Deeks is shot in "Personal", he is asked to provide a list of possible suspects. He includes a man named Gordon John Brandel as one of them, and it is later revealed that Brandel is his father: a man who frequently abused Deeks as a child until Deeks shot him (non-fatally) when he was 11 years old. Hetty asks Nell to find Brandel, and she discovers that he died in an auto accident in 1998 after being released from prison. (This, however, contradicts statements made in the earlier episode "Borderline", in which Deeks told Kensi that at Thanksgiving dinner six years earlier, his father had fired a shotgun at him. The contradiction brings into question whether Deeks's father is still alive or not.) When Deeks asks Hetty who he should list as his next of kin, Hetty gives him her name.
Deeks is extremely personal about his choice of firearm, preferring the LAPD Beretta 92FS over the NCIS standard-issue SIG Sauer. As stated in the episode "Bounty", this is because the 92FS's "manual safety saved ass one time during a gun snatch attempt by a junkie".
In the episode "Plan B", Deeks's best friend, Ray, tells him that he knows he has "a thing" for Kensi. He knows this by observing numerous interaction between the two. Though Deeks denies that he has "a thing" for Kensi, he blushes and he can not stop smiling while telling Ray that he does not have a thing. This leads some people to believe that Deeks may have feelings for Kensi. Ray says for Deeks to call him as soon "as things work out with Wikipedia" (Kensi). Near the end of the episode, Kensi asks Deeks if he is ever going to call Ray anytime soon. He walks close to her, then pulls back to look at her, then he smiles and says, "Why do you ask?" She said she was just wondering and when he does tell him that Wikipedia says hi, he laughs; and then Kensi says that she is glad that their "thing" is working out. Deeks once again denies any feelings he has for Kensi. In the next episode, "Imposters", a waitress asks Deeks if he and Kensi are a couple, Deeks says they are but Kensi is surprised and denies that they are together.
In the season two finale, Deeks proves his loyalty to the team. When Callen, Sam and Kensi resign so as to go rescue Hetty in Prague, Deeks tells Director Vance that he would resign if he was an NCIS agent before leaving with the team to go and help Hetty.
In "Touch of Death", it is hinted that Deeks is afraid of needles as he was heard screaming in agony as Hetty gave him an injection against smallpox before passing out from the shock of it, causing an amused Sam to remark, "Man down".
In "Neighborhood Watch", Kensi and Deeks go undercover as a married couple. Hetty has a talk with both of them about feelings that arise when two agents go undercover as a couple. The two laugh at the idea of having any kind of romantic feelings for each other, but their reactions are different. They play up the role, as their usual bickering goes very well with their current assignment together. They refer to each other as husband and wife, while in private they use their undercover names. This is unusual because throughout the episode, they are shown talking to ops inside their cover house. Deeks and Kensi have an awkward, yet enjoyable, confrontation with each other inside the cover house. Deeks walks in on Kensi in the bathroom, he in his ridiculous workout outfit and Kensi in a towel. After a brief conversation about her making him worry about her, they stand awkwardly. Kensi tells Deeks to take off his fanny pack (he calls it his "bro-sack") because it looks ridiculous. Deeks, not understanding what Kensi was referring to, starts to take off his pants. Kensi freaks, and Deeks enjoys the situation. Also when Kensi talks about starting a family, he says that he could do that for her since he was her "husband". It is uncertain if he was talking about this through his cover or if he was actually talking to Kensi.
After many tending and caring moments in season 4, Deeks finally makes his feelings known in the season 4 finale. Kensi accuses him of poor communication skills and "never saying what he means", but Deeks cuts her off her complaint with a kiss and then says, "How's that for communication?" The kiss leaves Kensi dumbfounded and she drives away. The season finale ends with Deeks and Sam being tortured.