I believe in Illinois you can't finish one off after a deer vsvehicle accident. Only law enforcement is able to. In my opinion that is a stupid law........I see pros and cons,the con beingthe deer laying there suffering. And the pro being yahoos killing injured deer off a busy highway in front of sensitive prople, although these type of accidents don't always happen in the more populated areas. I will say that I would rather put the deer down than worry what people think and if they knew the circumstances I'm sure they would be in agreement but who knows? I've seen it happen two times. Once outside my town a spike buckgot hit and broken down in the back, Some guy stopped along with others and was able to tie the deer up to a tree against my recommendations and attemped to slit it's throat. At the time I was on a fire department and had already radioed in to county and a officer was on his way. I couldn't get the guy with the knife to understand the law so I left. The second a deer had wandered into town and was struck, basically the same kind of injury. Luckily a state troppper was just leaving his house and stopped to take care of this one. But he had to get permission to discharge his weapon from his commander. As hunters we know a slow death is not what we want for the deer.