HARTFORD - The families of nine people killed in the December 2012, Sandy Hook School shooting incident and one of the survivors are seeking to have the Connecticut Supreme Court reinstate their "wrongful death" lawsuit and send it back to state Superior Court for a jury trial.

Late last year, the Supreme Court agreed to review the plaintiffs' request for the lawsuit's reinstatement, following a Superior Court judge's decision last fall to dismiss the legal action. Bushmaster Firearms International, LLC, is the defendant.

On the morning of December 14, 2012, a gunman shot his way into the school where he rapidly shot and killed 20 first graders and six adults, before killing himself as police approached. The gunman had killed his mother at their Sandy Hook home before going to the school that morning.

The plaintiffs' dismissed lawsuit alleges, in part, that the semi-automatic military-style rifle used in the shooting was negligently entrusted to the public, and that the defendant violated the Connecticut Unfair Trade Practices Act (CUTPA) in aggressively and unethically marketing the rifle to the public.

Last week, attorneys for the plaintiffs filed a legal brief through which they seek to have the Supreme Court reinstate the lawsuit.

In that 62-page brief, attorney Joshua Koskoff, representing the plaintiffs, wrote that the military-style semi-automatic rifle, commonly known as the AR-15, which the 20-year-old gunman used at Sandy Hook School, is a weapon of war.

"The AR-15 is an instrument of war. Designed for the battlefield, it was engineered to meet the exigencies of close-range, highly mobile combat," he wrote. The rifle is lightweight, easy to use, and produces high-velocity fire with limited recoil, which pierces helmets and body armor, causing severe wounds without the need for careful aim, he wrote.

The AR-15 also is known as the M-16. Bushmaster's version of the rifle is known as the XM15-E2S. The weapon has a high-capacity magazine for prolonged assaults, Mr Koskoff wrote.

"The weapon's functional virtues, so well adapted to the battlefield, pose catastrophic risk to pubic safety," he adds. The rifle's firepower is unnecessary for and inconsistent with civilian use, he wrote.

In the legal brief, Mr Koskoff further argues that the firearms company has opted to market its version of the AR-15 "as a weapon of assaultive violence," with younger males being the weapon's "desired demographic."

The gunman used the rifle to fire 154 rounds in the school in five minutes, killing 26 people there, the lawyer added.

The families' appeal asks the Supreme Court to consider the scope of the common law of negligent entrustment in Connecticut, and its application to circumstances and technology that could not have been contemplated when applicable state law was enacted, according to the plaintiffs. In the appeal, the plaintiffs argue that the meaning of certain language in CUTPA must be determined by the Supreme Court.

Through their lawsuit, the plaintiffs seek monetary damages, punitive damages, attorneys' fees, costs, and injunctive relief.

Lawyers for Bushmaster have two months to file a reply brief to the Supreme Court.