I wouldn't say several minutes later, but it's easy enough to believe you can get into your car with your friends and not necessarily look right at them as it happens. Maroni, the driver and one of his goons all were getting into the car...as they no doubt did on a regular basis. It happens Dent yanks the goon (I assume knocks him out), takes his place in the car and Maroni doesn't really notice, at first.I have a hard enough time believing that Maroni would get in the car and not notice Harvey right away. Now you're telling me he got in and didn't look to his left until several minutes later? Or that he got in, someone got in next to him after a little bit, and he again didn't look at the person?
C'mon now, think things through.
I figure they only just started driving when Maroni finally realized it was Dent.

