Richard Kimble: I didn't kill my wife!
Sam Gerard: I don't care. (00:37:10)
Richard Kimble: Do you remember what I told you in the tunnel?
Sam Gerard: Um, yeah. It was noisy, I think you said something like you didn't kill your wife.
Richard Kimble: Remember what you told me?
Sam Gerard: I remember you pointing my gun at me.
Richard Kimble: You said "I don't care."
Tracing tech: He's on the south side.
Sam Gerard: Yeah. Yeah, that's right, Richard. I don't care. I'm not trying to solve a puzzle here.
Richard Kimble: Well, I *am* trying to solve a puzzle.
Cosmo Renfro: Five seconds to location.
Richard Kimble: And I just found a *big* piece.
Answer: When Richard changes the diagnosis, the first thing he writes down is "AO" which is medical shorthand for aorta. Many people who have medical degrees and saw the movie speculate that Joel had an aortic tear. This would cause blood to flow into the chest cavity making it difficult to breathe and with the impact from the crash it could have caused the fatal injury. An aortic tear requires immediate surgery and by changing Joel's diagnosis, Kimble was able to save his life.