The civil suit that you alluded to seems to be out of line with the law as I know it although I have not had time to research gun owner liability on the civil side of the law.
Obviously, the statute requires that guns be kept locked up and out of reach for easy access; now we have trigger locks required as well.
If we keep in mind that there is an imposed duty to safeguard against the use of one's weapons (a factual determination) then there is a consequential duty imposed by the law.
If the failure to abide by this duty sets in motion an event or chain of events which results in death or injury (the efficient and procuring cause)then there would be tort liability to the injured or the estate of the decedent for wrongful death.
Much like our prior topic of the duty to retreat in one's home, we are left with what facts are sufficient to constitute negilgence in failure to protect in one's home against unauthorized use of our property.
One would think that it would be enough to lock a gun case and keep it in a closet not open to house guests and certainly not to felons obtaining the same by B&E.
Here again is the application of the "reasonable man" rule to a set of circumstances, which once outside of the thin language of the statute, requires fact finders to make subjective judgments.
Like any other matter of this type, you could try the case in front of several tribunals including law school moot courts and arrive at many different conclusions.
And all this without even a discussion on the role of the person who engaged in the unathorized use of the weapon!
Imposed liability of this type are a bitter pill to swallow, but are the halmark of cradle to grave legislators.
This mornings news disclosed that Massachusetts legislators want to pass stringent laws in requiring the use of filters to prevent children from inernet access to what ever these thought police can dream up.
Angry parents were quite incensed with this, and in my opinion justly so.
They want to usurp the rights of parents in raising their children, and the parents are at last getting angry at the intrusion.
None of us advocate easy access of our children to distasteful or disgusting (for children) literature or viewing; but the line must be drawn to prevent the erosion or our freedom. Orwell, you were right even if your time line was a bit off.
Ah, but that is the soap box of this old lawyer.