So-called smart guns are not a workable idea, because the technology available is not capable of producing such a thing.
First, all biometric modalities, including finger print and palm print scanners, have a non-zero false accept rate (FAR) and false reject rate (FRR). A biometric system must be fine tuned to balance security with usability, which is fine for authenticating users of a computer system, but not acceptable for a firearm.
Second, consumer electronics in general are garbage and have nowhere near the reliability of a well made handgun. For any given electronic device, a significant fraction of them will fail every year. Firearms can last for decades or longer, provided they are maintained. Consumer electronics are not maintained, they are thrown out when they break.
Finally, what people like this don't seem to understand is that a safe gun must always fire when the trigger is pulled, as well as never fire when the trigger is not pulled. The first is just as important as the second. A legitimately held firearm, whether held by a soldier, police officer, or private citizen, is a safety-of-life critical instrument that must operate correctly when it is used, otherwise the user is likely to be killed himself.
This is the usual "smart gun" bullshit, which wouldn't make an appreciable positive difference in the situation.
For one thing, it's telling they start out with a lie. Safety, if used honestly in this context, refers to preventing accidents, which are an "official" 600 deaths per year problem (scare quotes because I know criminal homicides that are scored as "accidents" for the usual political reasons; details on request).
The real issue is intentional homicides, i.e. guns being as designed. Note we're talking about a nation with > 300 million existing old fashioned guns in civilian hands, where in the last ~40 month every month except for last August has seen greater sales than the previous month a year ago, currently running at a million a month. Note that with a very minimum of care guns are functional for decades and decades: I would not feel inadequately armed with a Mauser 1898 (sic) rifle made in that year or soon after, and my teen centerfire hunting rifle was sporterized surplus Springfield 03A3, designed in 1903 (using a few Mauser patents :-) and manufactured during WWII. The 3rd most recent gun I bought was a M1 "Get Off My Lawn" Garand made a few months after Pearl Harbor (and boy does a part of me wish I hadn't sold that masterpiece of then cutting edge technology to buy a lighter rifle more suitable for my RSI injured arms).
The conceit that somehow these new, expensive and less reliable smart guns will displace the barest fraction of the above existing ones is ludicrous. Even if you take a long view, it would take centuries.
Then there's the laws, like fanatically anti-gun New Jersey's one that once there's a "smart gun" on the market, civilians will only be able to buy it. But, somehow, the Only Ones AKA the law enforcement officers who our betters insist are the only ones who can be trusted with guns (https://news.ycombinator.com/item?id=6680266) will be allowed to retain their old "unsafe" guns. Perhaps because everyone knows they'll be a lot more reliable.
In a county where almost every state has a shall issue concealed carry regime (obviously excluding most of California for now---the object lesson of Illinois should give you pause if you're happy with that state of affairs), adoption of these inherently more complicated and therefore less reliable guns would surely result more of the wrong people being shot. Although one could assume from how this is portrayed that to the extent the backers of this are engaging in rational thought they score all "gun deaths" as the same.
Let me make this as a bottom line closer: if you think there's fierce opposition to Obamacare, just try to push these on an unwilling population....
For hunting and pest control purposes, essentially (details on request, but being humane is obviously part of it).
For dealing with two legged snakes, not per se. Ignoring high energy (not .22 rimfire) rifles (can address that later if you wish), for normal handguns in self-defense, what police and civilians can legally do is stopping a lethal threat. Killing is not and cannot be the objective.
And there's basically three mechanisms for that, only one of which is reasonably guaranteed to work with normal human marksmanship.
First, when shot once, a large fraction of people will stop their aggression, e.g. Trayvon Martin is the most recent famous example. For that matter being shot at is often sufficient (browse YouTube some). But you obviously can't count on it.
Hitting the central nervous system, brain, or spine high enough, will do it. But those are small, hard to hit targets, we have strong instincts about threats to our heads, the brain is well protected with bone, etc. etc. ... and of course a hit to the brain is often fatal and almost certainly catastrophic.
Failing that, causing someone to lose enough blood they can't keep fighting is what you're left with---but that's dicey, there are many many incidents where e.g. heart function is outright stopped and the aggressor continues to be lethal for 10s of seconds to in some rare cases minutes. And this mechanism is obviously also hard to keep from going all the way to fatal.
One very special case for police snipers is the hostage situation where they have to hit the perpetrator's brain stem to prevent him from reflexively killing his hostage. That's invariably lethal (killed JFK), but still based on the, in this case, narrow legal distinction that the intent was to stop the perpetrator from killing a innocent 3rd party, not kill him per se.
Ah, I should add the deterrent affect. Being maimed or killed by a civilian is about the greatest fear of criminals according to surveys; the fact that the civilians will be using lethal guns is of course behind that. From that it logically follows that the vast majority of the 2.5 million gun self-defense incidents in the US every year do not involve anyone getting shot, and almost always even a shot being fired (warning shots are pretty much never legitimate).
Maybe not, but I decided to do a "Just the facts, Ma'am" posting ... and since so many are using the Martin case to attack the very idea of self-defense---and don't say that's silly, for the U.K. effectively outlawed it in the courts in the '50s, by statute in the following decade or two---I don't think it hurts to repeat the well established fact that he was the aggressor using lethal force on Zimmerman when the latter was forced to shoot him.
If you want to dive into that case, it's also telling he only shot Martin once (because Martin immediately ceased trying to kill him). That doesn't really jibe with the bogus narrative.
First, all biometric modalities, including finger print and palm print scanners, have a non-zero false accept rate (FAR) and false reject rate (FRR). A biometric system must be fine tuned to balance security with usability, which is fine for authenticating users of a computer system, but not acceptable for a firearm.
Second, consumer electronics in general are garbage and have nowhere near the reliability of a well made handgun. For any given electronic device, a significant fraction of them will fail every year. Firearms can last for decades or longer, provided they are maintained. Consumer electronics are not maintained, they are thrown out when they break.
Finally, what people like this don't seem to understand is that a safe gun must always fire when the trigger is pulled, as well as never fire when the trigger is not pulled. The first is just as important as the second. A legitimately held firearm, whether held by a soldier, police officer, or private citizen, is a safety-of-life critical instrument that must operate correctly when it is used, otherwise the user is likely to be killed himself.