Innocent until proven guilty.
A self defense homicide is a homicide.The DA does not have to prove you killed the guy.That is a given.The burden of proof is on the shooter,to prove self defense.A positive drug test will not help you.
The prosecutor must prove everything beyond reasonable doubt. You do not have to PROVE anything, the state must prove everything. Of course the news media will try you in the court of public opinion and spin everything so as to put pressure on the prosecutor.