What the hell are words on paper going to do for you standing over 4 unarmed dead bodies with a pistol? A corpse can't really confess to planning to mug you now can it?
Look, not wanting to argue here.
If you read before, once you are down one to one, if they are not armed with a gun, disparity of force is no longer in effect. Further you may not have killed the other three, or even had to shoot the others. You are trying to stop the threat so it doesn’t automatically mean they all are dead.
And I would hope you follow the advice given in my carry class, to always have a recording device running on your belt when you are out in public. I have a great digital recorder that I can plug into my USB port on my laptop and save the files.