As a law enforcement officer I just have to chime in on this one.
1. If you smack a deer or find a dead one you have two options, take it all or leave it all, but you have to have a salvage tag issued to you by someone before you move anything.
2.If you decide to skip step A, be sure that set of horns your cutting off is worth $4,000 to you, even if you dont get to keep them, because you won't. Ok, you probably wont get fined the $4K for just cuttting a roadkill, but you definately won't get to keep them, and you had better convince the officer that finds you that you didnt kill that deer or your back to $4k.
3. Yes, you can get a salvage tag for a deer that is intended for human or animal consumption. I.E. we have given numerous tags for people who have mountain lions and coon dogs. It is best to be put on a list for this (most countys have a list going) instead of waiting until you find the WR hit by grandma to decide your going to feed your hamster deer meat. (See #4.)
4. There is nothing on the books in Iowa that I am aware of that entitles the responding officer to any part of the deer over you, (if there is please let me know!) unless something looks suspicious. In which case, that doesnt make the rack his personal property but he will most likely hold on to it as evidence until everyone is satisfied. (Hint, discretely hacking antlers off in the ditch by moonlight looks kind of suspicious.)
5. Never, EVER, take it upon yourself to shoot a wounded deer, ESPECIALLY A BIG BUCK, without first calling law enforcement. (See #4.) I have seen this many times and it never fails to look at least a little suspicious despite the fact that most guys have good intentions.
6. Keeping the deer is not a reward for running over it. I only mention this because of my favorite car vs. deer story. I got called to an accident and the guy wanted to keep the deer. This particular deer looked very much alive and the fellow wanted to know if he should just cut its throat or if I should shoot it. I replied "I think I'll shoot it, but you might want to have your son get off of it first". The guy protested for a while but the boy eventually got off the buck, which immeadiatley jumped up and hauled the mail into the next county. The deer looked fine, the boy looked exhausted, and the old man was clearly PO'ed by the whole deal and could not understand how I could let his deer get away.
I really think 99% of these stories about CO's and police officers getting rich off of roadkills are bunk. Personally I have only seen one remotely large buck killed by car and the guy who found it got to keep it. Its just not that hard. Ask and you shall recieve, if not ask why. If you are not satisfied with that answer, ask his boss why. Chances are you will get it if in deed it is fair game. Or, you could just carry around $4,000 with you.