Interesting opinion easyg, but this is a case where evidence is ephemoral, at best. Testimony, of you, of the "others," of the responding officer, and of the 911 tapes is probably all the authorities have to go on in the matter.
Attitude and actions following the event can count for a lot.
Will you be detained? Will you be arrested? Will this go to trial? Will you be convicted by a jury?
All can be affected by how you present yourself and what you do in the moments following the altercation.
If you contact the police, voluntarily meet with an officer, give a statement, and appear helpful and honest (not saying too much, of course) you've done a lot to establish credibility and identity as the wronged party.
It is possible that the other party has also contacted law-enforcement as well (though in the original post scenario, probably unlikely). Now there are competing sets of testimonial evidence. But absent your contribution, the other side's evidence is all the cops have to work with.
And, if there is evidence of a prosecutable offense, the record of your 911 call will be played in a trial. That's your voice establishing your fear of the situation and your mindset at the time. Without that evidence on file you may find yourself listening (along with the jury) to only the other 911 calls made -- about YOU. (
"OMG, this guy just pulled a gun on my boyfriend...!" etc.)
Any cop who actually thinks that whoever called first must be "the victim" is a complete idiot.
Of course I didn't say "must be 'the victim.'" I said that your actions in seeking out the police and reporting a crime or attempted crime can certainly benefit you. Of course if there is evidence and it indicates that your story isn't true, a good officer isn't going to persist in believing you to be the innocent party. But you didn't really think I said that, did you?