Bill left the same party as margaret, but decided to sleep it off in the local park. the weather got cooler so he turned his car on to keep warm. the police found him asleep in the back seat. bill argues in his trial that since he was in the back seat, it was impossible for him to be considered ___ the car.

Bill argues in his trail that because he was in the back seat he couldn't have been operating the car.

Explanation:

Let's look at the situation. Bill was asleep in the back seat of the car. So he was unconscious. He couldn't drive the car asleep. He was in the back seat but we don't know what was his posture of rest. However, what we also know is that the car was turned on. It is never specified if there was someone else in the car because it is never said. But we can't also assume he was alone. The paragraph also doesn't specify if he left alone. So he could have been accompanied. there are many data lost in this paragraph. But the major fact here is that the car was turned on and it could represent a very big danger to society and Bill himself. That is why it is irresponsible from his part.

The answer is:

operating

Completing the sentence and filling out the blank:

It was impossible for him to be considered operating the car.

It was rather impossible for him to be operating the car because as mentioned above, he was at the back seat and who else will operate a car in the back seat.