If you care to read it, the main case on shooting fleeing felons is Tennessee v. Garner. Link here:
FindLaw | Cases and Codes
The key holding is this:
"Where the officer has probable cause to believe that the suspect poses a threat of serious physical harm, either to the officer or to others, it is not constitutionally unreasonable to prevent escape by using deadly force. Thus, if the suspect threatens the officer with a weapon or there is probable cause to believe that he has committed a crime involving the infliction or threatened infliction of serious physical harm, deadly force may be used if necessary to prevent escape, and if, where [SIZE=-1][/SIZE] feasible, some warning has been given. As applied in such circumstances, the Tennessee statute would pass constitutional muster."
In the criminal case, my argument would be that the suspect first lied to the officer during the traffic stop, then, when the officer went to go run his identity, the suspect took off running from the car. When the officer caught him, the suspect physically resisted arrest, including grabbing at his taser. The officer, in the split second he had to make a decision, reasonably believed that the suspect, though not an immediate danger to him, had repeatedly demonstrated a willingness to engage in violent felonious contact such that the use of deadly force to prevent his escape back into public, was justified.
I only have to convince one of 12 people that there is enough there that reasonable doubt exists as to whether it was criminal to do so.