Chances are probably NO.
The serial numbered portion is the lower receiver, in addition, to actually match a casing collected to a casing from the rifle, you would have to have the same extractor, firing pin, hammer, etc.
I'm not an expert in the field of ballistics, but I'd say they (or WE) would want the whole rifle.
As far as taking pieces and parts off the rifle (like the Eotech or anything else), I don't see a problem with doing something like that, but then again, it's never been addressed. We don't let people take rims off cars, but if someone had a pull-out stereo they'd be able to take it with them.
Kind of a stange example, but it's the one that comes quickly to mind of things that get impounded/stored most often.
ETA: Also, is it the proliferation of TV shows that everyone thinks guns are going to be taken for ballistic testing when you are ADMITTING to having shot someone with a particular gun for a particular reason?