Based on my experience as a 45-year Las Vegas gun shop owner, firearm background checks are ineffective. While the false positives run about 5% — usually because of a similar name, place or date of birth — the actual denials are less than .05%. Any research based on real data shows that criminals virtually never go through any background process to obtain their tools.
Most criminals get firearms from other criminals, who steal them from anyplace firearms are kept, most often in burglaries from private homes.
President Donald Trump is backing “tighter” background checks for gun purchases, but said he wants to be careful that closing what he calls “loopholes” doesn’t clear the way for unconstitutional restrictions.
The biggest loophole is the HIPAA rule that prevents looking at mental health histories of would-be gun owners. Mental health data is private. Another is that juvenile criminal records disappear for young criminals, reformed or not, when they reach age 18 or 21.
Nobody wants truly dangerous, mentally ill people to obtain firearms. That said, any modification of these constitutional rights is the ultimate slippery slope that must be handled very carefully. A speedy, (72 hour?) judicial review of any denial wherein the would-be buyer and his or her attorney is present is appropriate at the bare minimum.