Harmon Rabb Junior was a long-time JAG officer and a Navy Commander who defended and prosecuted various Marine and Naval officers accused of committing any kind of crimes from drug smuggling to murder.
Originally a naval aviator, Harm was forced to give up flying due to night blindness although it was later revealed that the night blindness was later revealed to have been a misdiagnosis.
After a few years as a Judge Advocate, he had laser surgery to correct what was misdiagnosed as night blindness (actually blurred vision as a result of retinal scarring caused by service action) and resumed his career as a naval aviator, flying F-14s off the USS Patrick Henry (CVN-74) as a member of VF-218 "Raptors".
As a result of his father, Harmon Rabb Senior getting involved with a Russian woman whom his father also died protecting after Harm Sr was shot down while flying over North Vietnam on Christmas Eve 1969, Harm has a half-brother named Sergei Zhukov who like Harm later fell under investigation for the death of Lieutenant Loren Singer and both siblings were suspected of fathering the baby Singer had been pregnant with when she'd died.
NCIS Special Agent Leroy Jethro Gibbs even initially thought that Rabb was the culprit and as such, Rabb was arrested and brought to the brig but Gibbs's colleague, fellow NCIS Special Agent Anthony DiNozzo was successful in proving Rabb's innocence while bringing Lt. Singer's real murderer to justice.
During a talk with fellow NCIS Special Agent Vivian Blackadder, Gibbs admitted that Rabb was the best defender and prosecutor that JAG had which implies that Rabb is one of the most skilled lawyers the JAG team has, Harm's skills even surpassing those of Harm's partner, Marine Sarah MacKenzie and Harm's friend, Lieutenant Bud Roberts Jr.
- David James Elliot who plays Rabb originally hails from Canada and in real life, is also married to Nanci Chambers who played Lt. Loren Singer.