Photo: The Canadian Press

Ian Hockley, front left, father of Dylan Hockley, one of the children killed in the 2012 Sandy Hook Elementary School shooting.

Newtown school shooter Adam Lanza heard the message loud and clear when gun-maker Remington Arms marketed an AR-15-style rifle as an overpowering weapon favoured by elite military forces, a lawyer for relatives of some victims of the massacre told the Connecticut Supreme Court on Tuesday.

Lanza, who killed 20 first-graders and six educators with a Bushmaster XM15-E2S on Dec. 14, 2012, was obsessed with violent video games and idolized the Army Rangers, attorney Joshua Koskoff said.

Koskoff asked the high court to reinstate a wrongful death lawsuit against Madison, North Carolina-based Remington. He said the Bushmaster rifle and other AR-15-style firearms were designed as military killing machines and are too dangerous for the public, but Remington glorified them and marketed them to a younger demographic that included the 20-year-old Lanza.

"Adam Lanza heard the message," Koskoff told the justices, whose decision isn't expected for several months. "They marketed the weapon for exactly what it was. They used images of soldiers in combat. They used slogans invoking battle and high-pressure missions."

The case is being watched by gun rights supporters and gun control advocates across the country as one that could set a precedent in cases accusing gun-makers of being responsible for mass shootings. Several groups including the National Rifle Association and emergency room doctors submitted briefs to the court.

At issue is a 2005 federal law that exempts gun-makers from liability when their products are used in crimes, and two exceptions to the law.

One exception allows lawsuits alleging "negligent entrustment": when companies know, or should know, that their weapons are likely to be used in a way that risks injury to others. The other allows lawsuits alleging manufacturers knowingly violated a state or federal law that applies to the sale or marketing of firearms.

The plaintiffs in the case — a survivor and relatives of nine people killed — sued Remington in 2015, citing the negligent entrustment exception and claiming the company violated a Connecticut law against unfair sales and marketing practices.