And thats what QD mounts are for. It doesnt have to be on there when anyone gets there.
It is inadvisable, and almost certainly illegal to alter the scene of a crime intentionally. If it comes out--and there's a reasonable chance that it could--it would be considered as evidence of guilt. (Remember that any shooting is the scene of a crime unless it is accidental--in which case it might or might not be criminal.) Even if the shooting is justified, a crime was still committed (by the attacker) or there would have been no justification for the shooting.
If, for example, the shooting takes place at close range, stippling on the attacker should be evident. If there is none (and there probably wouldn't be with a suppressor), that would call defender's version of the events into question.
Do not, under any circumstances, alter the scene of a shooting before the authorities arrive unless it is obviously necessary for safety or to treat a victim. That's if you are innocent. If you murdered someone then I guess that's a different story.
Ok, to the original question:
IF the situation is clear-cut, the suppressor would probably not be a legal issue. If, there were any questions about the circumstances of the shooting, I think the use of a suppressor could be a complicating issue in a legal defense. It's going to be pretty easy to spin.
1. The media (both in terms of news and entertainment) tend to be very negative about silencers and a lot of people get their views from the media. They are portrayed as being used primarily by criminals--an incorrect portrayal, but still one that has shaped the views of hundreds of millions of potential jurors/grand jurors.
2. Many people believe silencers are outright illegal--and, in fact, in some places they are. Even where they are not illegal, they are still heavily regulated and the laws are not well understood, even by most in the gun community.
3. People are unlikely to be able to identify with silencer owners/ users because there just aren't that many silencer owners out there, in the overall scheme of things. In TX (where there are more silencers owned than in any other state), only about 0.6% of the population owns one. Even amongst gun owners in TX, fewer than 2% own silencers.
As far as the utility of silencers goes, there are some things to consider:
1. If you are the only person who fires a gun in the situation, then, yes, it would be much better for your ears. Unfortunately, if the attacker has a firearm, it's highly unlikely that their firearm will be suppressed.
2. Suppressors tend to negatively affect the reliability of typical locked breech/floating barrel handguns. They shouldn't have any effect on fixed barrel designs, but those aren't common in calibers above .380ACP/9mmMak. If I were using a suppressor on a floating barrel handgun for non-recreational purposes, I would want to spend a good deal of time insuring that the suppressor/handgun/ammo combination was adequately reliable.
A justified shooting in your "castle" ends with no possibility of a civil suit.
That's what the law says.
I asked a lawyer who is very involved in gun rights what would be adequate proof that the shooting was "justified" and he admitted that the law was vague on that issue and it was not possible to say with certainty.
He felt that being tried and acquitted would almost certainly constitute proof that the shooting was justified, but didn't know if simply not being prosecuted would be accepted as proof--or even if getting a no bill from a grand jury would.
Just something to keep in mind. Things are often more complicated than they initially seem.