Defending and Murdering (Dev Suggestion)

I for one don't even know if this is possibly or how hard it would be, but let's say someone takes you on but you defend yourself, and kill the guy, in chat it could say, so and so defended themselves against so and so, instead of murdering, because then even if you are defending, people will still treat you like a murderer, unless they know the hole story. Some people just see two people fighting, wait for one to died then jump in and kill the winner because he is a murderer, but in reality he was just trying to defend himself...

Yeah it's sounds all really confusing, but it's just a small idea to try to separate good guys and the bad guys.