The 10 Newtown plaintiffs argue that the AR-15 is a weapon of war — its cousin, the M-16, was the rifle of choice in Vietnam — and therefore should never have been marketed to civilians. They say, in effect, that the availability of a high-velocity weapon capable of inflicting such rapid carnage constitutes such negligence.

“The novelty of the approach is that it doesn’t depend upon an argument that the manufacturer knows that a particular shooter is a high-risk buyer,” said Heidi Li Feldman, a professor at Georgetown University Law School, who has followed the Newtown litigation. “The novelty is that it substitutes the general public for a particular individual.”

The timing of the attack in Orlando, where 49 people were fatally shot, may invigorate and inflame the legal challenge against the gun industry. Gun-control advocates and victims’ rights groups have embraced the case as a way to knock down stalwart gun protections, while gun makers and dealers are watching the case intently.

Eighteen months after it was filed, the lawsuit — naming the manufacturer, Remington; the wholesaler; and a local retailer — is still in the early stages. But the case has not yet been tossed out of court. Even some plaintiffs were startled when Judge Barbara N. Bellis of State Superior Court, who has yet to rule on a final effort to quash the case, set a trial date — two years from now — and ordered the defendants to disclose marketing materials and other internal documents.

Image The Bushmaster AR-15 rifle that Adam Lanza used in the Sandy Hook Elementary School shootings in 2012. Credit... Connecticut Department of Justice, via Reuters

Also central to the case is the way that gun makers and dealers promote assault rifles. Just before a hearing in April, Bill Sherlach, whose wife, Mary, a school psychologist, was killed in the Sandy Hook shooting, said he was eager to see company memos.

“We look forward to the discovery process, where we can see what goes on behind the curtain,” Mr. Sherlach said outside the courthouse in Bridgeport.

The defendants have been vigorously seeking to have the lawsuit thrown out, and they have one last chance at a hearing on Monday in which both sides will make their cases. The judge has until October to decide whether the case will go to trial.

The gun companies had asked Judge Bellis to delay the discovery phase until she ruled on the defendants’ motion to strike the case. The judge denied the defendants’ request, saying that the plaintiffs had waited long enough and that the parties should start exchanging information immediately.

Image Mark and Jacqueline Barden with their children. Their 7-year-old son, Daniel, center, died in the Newtown shooting.

The Sandy Hook families’ legal team has requested numerous documents relating to the marketing of the AR-15, as well as the companies’ desired customer base and use of video games for promotion, among other things.

Mark Barden recalled watching his wife, Jacqueline, at the computer in the first weeks after their 7-year-old son, Daniel, died in the 2012 shooting. “She was trying to research how the kid around the corner got his hands on a military rifle designed for combat,” Mr. Barden said, “and carried it into our son’s school to murder him.”

Using an AR-15 model known as the Bushmaster, Adam Lanza, a disturbed 20-year-old who lived near the Bardens, shot his way into Sandy Hook Elementary School. In less than five minutes, he fired 154 rounds. His mother, Nancy Lanza, whom he also killed, had legally purchased the weapon.

The Bardens were stunned, they said, to see how gun companies advertised the weapons online to the general public, using militaristic language and macho phrases like “Get your man card” and “The opposition will bow down.”