Unfortunately, only on very old TV shows.  You need to watch more CSI and less Perry Mason!

Forensic analysis of the blood spatter evidence, gun powder patterns, microscopic analysis of the knife; all sorts of police investigations could reveal your attempt to alter evidence on the crime scene.  

When the DA goes to the Grand Jury to decide if you were justified in the shooting, this sort of thing will not help you.

I remember a case back in the day when a Chicago police officer's  'throw down knife' got him indicted because there was microscopic blue serge lint in the crack between the blade and the haft of the knife.  Matched police officer uniform blue serge precisely according to the crime lab analysis.

What do you think all those crime lab people are doing for a couple of hours or a couple of days at a homicide crime scene?  Videos, stills,  laser analysis of bullet paths based on the position of the body, however it falls.

Better to rely on the truth in this sort of thing.