I am going to answer and then run and hide. If you learn a deer's anatomy, like a physician. Actually pay attention when you skin it, or disect a buck after you cut his head off, you can learn to kill a deer a hundred different ways.I'm pretty much obsessive compulsive, so I have done this. I took my buck of a lifetime by shooting it in the neck. I took out both Carotid arteries and the windpipe at 12 yds. I was face to face and its body was partially obscured by CRP.It spun around twice and died in a pile.
I don't say do it, especially under duress in a hope that adeer won't get away. Don't be selfish....you don't have the right. But if you can take out the X at 20 yds, you can hit any spot that you know will kill an animal. A double lung shot is not the most humane, it is the easiest. A head shot is the most humane, but it is not feasible. Everything must be taken in context. There is no such thing as always or never......