The families of nine of the 26 people killed two years ago at the Sandy Hook Elementary School in Connecticut have filed a lawsuit against the manufacturer, distributor and seller of the Bushmaster AR-15 rifle used in the shooting. You can read the complaint here.
The complaint alleges that the defendants should be liable because they knowingly marketed a rifle to the civilian public that has little or no utility for civilian purposes. The rifle was designed for military purposes.
This type of claim is not totally new, and, unfortunately for the plaintiffs, similar claims have failed in the past. Also, it should be noted that in 2005, Congress enacted The Protection of Lawful Commerce in Arms Act to protect gun manufacturers from lawsuits for injuries caused by people using guns for criminal activity. Part of the motivation for the bill came from a case filed by the victims of a shooting rampage by a white supremacist who killed a number of people, including several children, at a Jewish center. The lawsuit claimed that the defendant made more guns than they could sell on the legitimate market with the intention of selling the remainder on the “secondary market” where criminals often buy their guns. In other words, the plaintiffs alleged that the manufacturer marketed the guns knowing they would be used for criminal activity. The lawsuit survived for a long time after the adoption of the Act, but was finally dismissed, in a 2-1 opinion, by a panel of the United States Court of Appeals for the Ninth Circuit.
The new complaint related to the Sandy Hook shooting is trying to distinguish the case from those older cases by framing the claim as an exception to the 2005 act, which recognizes a possible claim against someone who "entrusts" a weapon to another. I am not sure the allegations support that distinction.
In the end, the Sandy Hook complaint is based on the notion that the manufacturer knowingly placed in the market a gun that should not have been marketed because it did not have any appropriate use. That is similar to the old claims raised against the manufacturers of "Saturday Night Specials" and the "nuisance" claims used against manufacturers who continued to market guns knowing the market among civilians was saturated, etc.
Jonathan Turley has a comment on the case here (he thinks it has little merit). AboutLawsuits has a little more information here.
UPDATE 10-14-16: Several sources are reporting today that the lawsuit has been dismissed.