Isn’t the first thing to do in such cases is to check who in his primary and secondary circles has a licensed firearm? I am not detective, but that makes sense to me.
That could be any of hundreds of current and former students. It's not legal to do investigations like this since it ends up with a bunch of innocent people getting caught up in the surveillance dragnet, but they do it anyway and use a strategy called "parallel construction" to build a legal case against the suspect that coincidentally incriminates them for the primary crime.
No, that seems like a lazy technologist approach of reflexively hanging your hat on database queries. Police do actual police work like physically collecting evidence, seeing if they indicate any particular kind of gun or known ballistics, reconstructing the encounter, etc.
Also FWIW in MA firearms aren't licensed, rather their owners are. And ownership isn't registered, rather many types of transfers are supposed to be recorded.
You’re assuming I meant anything about checking against a database. I meant more that casings found at the scene should be compared to casing of bullets fired from guns of his known associates.
Granted, even if you find such matches, you still have to prove motive and opportunity.
It’s a little different for guns, they’re more tightly controlled and there’s often paper trail of their purchase and licensing of owners, so your example doesn’t apply.
I think there’s also the issue that you’re more likely to be murdered by someone you know than a random person. At the very least, matching bullet marks from shots fired from his associates guns to any casings found at the scene is just due diligence.
The reality of guns in the US is that a gun linked to a crime is likely to be part of a cohort of guns with a "short life to crime" having bounced through obfuscating straw purchases.
The most rapidly increasing (although still small in absolute numbers) class of gun associated with crime today are the 3D-printed variations:
Thousands of guns are found at crime scenes. What do they tell us?
So, yes, if this a crime of passion, a dispute between aquaintainces that escalated badly then there's a good chance the gun used has a history of ownership and registration.
If this is a crime related to home invasion gone badly then it's more likely to be a gun that fell off the radar some time past.
