Character mistake: When Gibbs first looks at the victim's body and sees his rank, he incorrectly refers to him as a Lieutenant when the rank is for a Captain.
Continuity mistake: When the victim's wife is asking if he will be exonerated, her grip on her cup changes between shots. (00:14:25)
Answer: I dont believe it is ever mentioned, but like most pilot episodes the characters are often changed, replaced or even removed in this case.