Why the case was brought-based on my speculative opinion
This theory may be similar to the Ford Pinto case, where design was such that it was not state of the art to place gas tank where located, resulting in more fatalities in collisions through explosions.
Or just imagine airbags NOT being federally required, yet all manufacturers provide them bar one or two.
There are better examples, no doubt.
Here the theory is that through a forseeable misuse the gun got into the hands of a 3 year old. The 3 year old doesn't know much and plays with the gun and is able to discharge the weapon, acting like a usual dumb 3 year old. Why is that? Why is it possible for an incompetent 3 year old little rug-rat to engage the weapon?
The gun has no true manual safety as we know it in the industry, and a 5# trigger pull. Had the gun had a safety it would arguably be safer and perhaps the incident would have been averted. Plaintiff would have an even weaker case and Glock would then have an even stronger case if such a manual safety existed.
Heck, if they require it for the Armed Forces, and now XD is coming out with the option, the argument is conceivable. It may or may not fly.
Here is why I believe the case was brought: we have Prop 51 in California, so if father is 99% negligent and Glock is only found 1% negligent it will be fully liable for 100% of lost earnings, future lost earnings, medical bills, future medical bills, and other special damages. (They have insurance for such things). However, Glock would only be liable for 1% of plaintiff's past, present and future pain and suffering, which includes emotional distress.
I think the plaintiff has a clever lawyer, and presented with the law, it would be foolish for anyone not to pursue the matter, given the position of this unfortunate man. The law in California is of 'comparative' negligence. 'Contributory' negligence on the part of plaintiff would have 'barred' plaintiff's claim altogether if plaintiff were only slightly negligent, even 1%.
But contributory negligence is no longer the law in this State. The Court felt it resulted in too many injustices, so now they apportion fault between the parties, with an apportionment for pain and suffering but full responsibility for medical bills, etc., if found 1% or greater negligent. There's insurance for such things. And I haven't heard much about insurance companies being in the red.
Given the law, it could be argued that a lawyer would be liable for professional malpractice in not bringing such a case if the retained lawyer let the statute expire.