What do criminals do after having committed a crime? They leave the scene as fast as they can, don't they?
You want to MAKE yourself look guilty? Leave the scene as you have described and every juror in the damn world will construe that action as an admission of guilt. The police will be well brassed off because they now have to find you, and lets be honest they only arrest the guy lying on the floor in exceptional circumstances, after all the loser in a fight isn't the one who was most aggressive.
I'll throw my hat into the ring with the police on this, they deal with this type of situation day in, day out and tend to know what they are doing. I uphold the law as best I can as a civilian. I suggest you may benefit from following suite.