I think the land owner would be considered the one that killed the deer in the eye of the law as he was the one who actually killed the deer. I personally wouldn't shoot someone else's deer that is mortally wounded to avoid these issues unless its obvious the animal is fine. If I can see a bullet wound from months ago than its not an issue to shoot it, but a mortally wounded animal can cause a big dispute. I believe its best to ask for permission for tracking on a property, if someone wants to ask for permission then fine and we'll even lend a hand. But if your just found wandering around our property were going to have an issue as as far as we know you may of poached the deer on our land, are trespassing, etc. We had someone search for a deer they shot on a neighboring property two weeks ago. They stopped by our home to tell us who they were, were they thought the deer may be, who's property they were hunting, time they shot the deer, etc. We gave them permission and gave the owner of the land they were hunting a call to verify them. They didn't find it but they asked for permission properly etc.