A couple things.
What the others have said is true, speaking through the filter of an attorney is going to be the best bet; keep in mind however that you don't need to already have an attorney in mind to call when you say you'd like to speak to an attorney before answering questioning.
However, there is some Massachusetts specific case law that you should be aware of when it comes to your right to remain silent and firearms law.
The courts have ruled several times that the burden of proof is on the individual to show that they are in compliance with licensing laws.
Commonwealth v. Irving Jones:
We sum up the established interpretation of G. L. c. 278, Section 7, as it applies to prosecutions under G. L. c. 269, Section 10 (a). The holding of a valid license brings the defendant within an exception to the general prohibition against carrying a firearm, and is an affirmative defense. Cf. Mass. Proposed R. Crim. P. for Dist. & Super. Cts. 11 (a) (1) (C), 11 (b) (1) (C), 14 (b) (3) (July 30, 1976). Absence of a license is not "an element of the crime," as that phrase is commonly used. In the absence of evidence with respect to a license, no issue is presented with respect to licensing. In other words, the burden is on the defendant to come forward with evidence of the defense. If such evidence is presented, however, the burden is on the prosecution to persuade the trier of facts beyond a reasonable doubt that the defense does not exist.
This was upheld in
Commonwealth v. Ben Seay:
In addition, we have held that the defendant has the burden of producing evidence to show that he was licensed or otherwise permitted to carry a firearm.
This thread also touched on the burden of proof WRT LTC's, and how one can be arrested if they have an LTC but don't notify the police.
Also, the Seay case also touched on the defendant's silence:
At a criminal trial, comments by the prosecutor, in his discussion of the defendant's evidence of entrapment during final argument, with respect to the absence of evidence concerning the defendant's frame of mind did not improperly call the jury's attention to the defendant's failure to testify.
Keep in mind that the courts found in
Patrick Godfrey v. Chief of Police of Wellesley that it's not arbitrary and capricious for a chief to find you "unsuitable" based on you invoking your right to remain silent:
A police chief's revocation of a person's license to carry firearms on the basis that he was no longer a "suitable person to be licensed to carry a firearm" was not arbitrary, capricious, or an abuse of discretion, in circumstances where the person had refused to cooperate with the police in their investigation of gunshots having been fired into a school, a private residence and an automobile.
Massachusett's gun laws are a complex mire of insanity. This alone is enough reason to consult with an attorney if you wish to own guns in Mass., but it's even more important when it comes to a self defense shooting.
So, if you're involved in an SD shooting in Mass., keep in mind that you still need to prove to the police that you are licensed, and if you refuse to answer questions, your LTC can be revoked.
I'm also wondering now if the "burden of proof" standard for licensing can be applied to pre-ban mags/rifles in Massachusetts...? For instance, requiring the defendant to prove that their mags are pre-ban, which could get very unpleasant if they don't have reciepts, or if they use Glock mags that Glock can't date (which is any without marking or the ambi notch).
Would any of my fellow Mass. law geeks care to get into this discussion with me?