There is a strong case to be made that anyone wanting to purchase and use a gun be psychologically evaluated before obtaining it rather than after they commit an act of violence. These types of evaluations are already in use for people in careers in which guns are part of the job description. Law enforcement, military, private security contractors, prison guard, and a number of other professions require both psych evaluations and training before anyone is hired and handed a gun.
Requiring individuals who want to purchase (or already own) a gun to have a psychological evaluation probability would produce test results that would look like this;
* The individual would be sexually insecure. With men a lot would have to do with size. The smaller the individual, ( I'll leave this to your interpretation) the bigger the gun. A clear sign of this personality type would be someone driving a Hummer with gun racks holding a couple of assault weapons and a nut sack on the trailer hitch.
* The individual is highly anxious, hyper vigilant, and, in severe cases, paranoid. These individuals never got over the fear of the childhood "boogeyman" their parents scared them with and "perceive" that their is a threat out there they need to protect themselves from. A clear sign of these symptoms would be someone who feels threatened by someone playing loud music in the car parked next to them.
These symptoms would apply to the average person which most of us would not consider dangerous. Many of them go into careers like law enforcement, the military, or join the CIA where they can safely express these characteristics because, in many situations they would be appropriate responses. Owning a gun is part of the job description which comes with training and education on how, and under what circumstances, it should be used. That is, situations that present a real threat It only becomes a problem if it carries over into someone's personal lives where they may "perceive" a threat and are unable to discern between reality and imagination. The majority of domestic violence occurs as a result of these dynamics
The next two categories are a different story;
* First there are the individuals with sociopathic characteristics. They are usually obsessed with power and control and have no sense of guilt or remorse when it comes to manipulating and exploiting others in their self interest. These are the folks that can read others like a book and play them like a fiddle. They tell you what you want to hear and will change their opinions without hesitation to get what they want. The "etch-a-sketch" analogy fits these individuals perfectly. These individuals thrive in a capitalistic, profit driven society such as our, and are often idealized and held in high regard; even by those they exploit. That's how slick sociopaths can become with practice.
* Then there's those individuals who we label "psychopaths" and are often described as "evil" or, in the most severe of cases, the Devil. These individuals are usually sociopaths at the start and, for reasons we still have a difficult time explaining, they transform themselves into monsters that defy rational explanations of the horrific acts they commit. Some say its a result of childhood trauma, or other extreme experiences that these individuals experienced at some point. These individuals are clearly devoid of feelings as we know them. When these individuals commit violent horrible acts there is no guilt or remorse, and in many cases, the true psychopath experiences euphoria or erotic pleasure.
The obvious benefit of requiring psychological evaluations for those who want to carry and use a gun is that there is a high probability that those who fit the profile in the last category would be quickly weeded out and possibly be placed on a "big brother" watch list much like the ones we use for terrorists who want to fly. Some would say that this would be a violation of "human rights" , but then, what about the victims, who because of societies failure to protect them, not only lost their "rights but their lives."?