@SundayDriverCatcher Here in the US any threats delivered by mail is a Federal crime, and while the USPS is too lazy to investigate, a lawyer with good connections can pressure the Cops to do more including fingerprint work. If the Cops can get enough evidence for an arrest and prosecution
then the USPS will follow with an investigation and invoke Federal charges on top of what the local laws do.
Federal sentences have no probation, parole, or early release Uncle Sam don't play that game any more
One landlord I've worked for had to do that to catch a ex-tenant who kept vandalizing his property; cost him about $250 he told me but the Cops came out, got prints, and that put the guy away as he wasn't supposed to be on the property
Normally here Cops don't even come out for simple break-ins anymore- they give you a case number on the phone for you to turn into your insurance company and that's it. Even with pics or vids. Only if you can tell them who the cams saw do they bother to lift a finger for you; they won't even look to see if it's a creep they know
Sad that you have to do the work you've already paid for the Government to do but that's how it is these days here in the US
If you don't have a good lawyer now get one; they won't be cheap, only worth it
If they tell you they can't do anything for you they're
not a good lawyer
Phil