After Shannon and Kelly's deaths and before he married his second wife, it is suggested that Gibbs had an affair with a woman named Rose Tamayo in Colombia.He was on a classified drug interdiction mission as a Marine Scout Sniper, and was wounded during the mission.
Aside from his tendency to use military slang, he rarely mentions or speaks at length about his time in the Marine Corps although he is often referred to as "Gunny" by other Navy and Marine officers, and has a replica of the iconic Raising the Flag on Iwo Jima photograph framed and mounted above the fireplace in his home.
In the season 4 episode "Singled Out", Mc Gee asks Gibbs how long he has been a special agent, to which Gibbs responds, "16 years".
In season 7, Gibbs meets lawyer Margaret Allison Hart (Rena Sofer), who worked for an old enemy of Gibbs, Col. Although Gibbs and Hart oppose each other over several cases, they are also attracted to one another.
When it was discovered that Bell was responsible for the death of Lara Macy in connection with the long-ago murder of Pedro Hernandez, Hart turned her back on Bell, showing her allegiance to Gibbs. Samantha Ryan (Jamie Lee Curtis), a psychologist with the DOD Psy Ops, who has collaborated with his team in several episodes.
This contradicts Gibbs' statement in the JAG season 8 episode "Ice Queen", when in response to Harmon Rabb's question, "How long have you been doing this, Gibbs? Gibbs holds service personnel in the armed forces in high esteem and to a higher standard.
He becomes particularly indignant when the guilty party is someone in a position of trust and authority and has reacted violently on several occasions when apprehending corrupt high-ranking officers who committed crimes for monetary gain.
to join the Marine Corps and did not return for over thirty years.
In a flashback scene in the episode, as a teenager, Gibbs often provoked violence with defiance to his father, who constantly comes to his unwanted aid with a Winchester rifle or shotgun.
Leroy Jethro Gibbs was born before 1959 as confirmed in the episode depicting flash backs referring to the death of Joan Matteson and the team focuses on disappearance of Lieutenant Flores in Afghanistan. Bellisario initially did not think Mark Harmon would fit the role of Gibbs, a "flinty type with a strong sense of honor and respect for the military", but changed his mind after viewing a tape of Harmon's portrayal of a Secret Service agent on The West Wing.
Harmon was cast in 2003, and Bellisario explained, "I said, 'Oh, my God, he's Gibbs.' He had matured. Mark Harmon is a Middle American guy, even if he was raised in Southern California. In an early episode, Gibbs "playfully smacked Weatherly's Dinozzo on the back of the head" resulting in the trademark "headslap" that later appeared in many episodes throughout the seasons.
In the season 7 premiere, "Truth or Consequences", he kills the terrorists holding his team hostage from an exceptionally long distance and in "South by Southwest" he outshoots a professional hit-man in an approaching helicopter.