Relatives of one of America’s most notorious school shootings have been told they can sue the manufacturer of the gun used to kill 26 adults and children at Sandy Hook.

In a decision that could have huge implications for a country where gun makers have typically been shielded from liability by a 2005 federal judgement, the Supreme Court in Connecticut said Remington could be sued over the way it marketed the Bushmaster rifle.

This was the weapon used by Adam Lanza to kill 20 youngsters and six teachers at Sandy Hook Elementary School in Newtown in December 2012. Lanza had earlier in the day killed his mother, and subsequently took his own life as emergency teams arrived at the school.

At the time, the shooting at Sandy Hook appeared to mark a new low for the nation when it came to gun violence and the 10,000 or so people who lose their lives to it every year.

At the White House, on the day of the shooting, Barack Obama wiped away tears as he updated the media. When he later attended a prayer memorial in Newtown, he struggled to find words that matched the gravity of the situation

Mass shootings in America Show all 8 1 /8 Mass shootings in America Mass shootings in America Camden shootings – 1949 Howard Unruh killed 13 people, including three children, during a 12-minute walk through his neighborhood on September 6, 1949, in Camden, New Jersey, when he was 28 years old. The incident became known as the "Walk of Death". Unruh was found to be criminally insane and died in 2009 after a lengthy illness at the age of 88, following 60 years of confinement. Alamy Mass shootings in America University of Texas tower shooting – 1966 Charles Whitman killed 17 people and injured 31 others in Austin, Texas. After stabbing his mother and wife the night before, he headed to the University of Texas, where he opened fire on people in the campus and streets from the observation desk. He was shot dead after a policeman and civilian reached the scene. Austin History Center, Austin Public Library Mass shootings in America Easter Sunday Massacre – 1975 James Ruppert killd 11 family members in his mother's house, which included his mother, brother and his wife, as well as their eight children. He used a magnum, two handguns and a rifle. Mass shootings in America Wilkes-Barre shootings – 1982 Former prison guard, George Banks, shot dead 13 people in Pennsylvania, including five of his own children. AP Photo/Times Leader Mass shootings in America Wah Mee massacre – 1983 Three men, Kwan Fai Mak, Wai-Chiu Ng, and Benjamin Ng, killed 13 people who were in Seattle's Wah Mee gambling club. YouTube/KIRO 7 News Mass shootings in America San Ysidro McDonald's massacre – 1984 James Huberty killed 21 people and injured 19 others after he walked in a McDonald's in San Diego. He was shot dead by a sniper after 78 minutes of him entering the restaurant. Alamy Mass shootings in America Palm Sunday massacre – 1984 Ten people were shot dead from handguns at close range in a New York home. A baby girl was the only survivor after convicted dealer, Christopher Thomas, shot three women, one teenage girl and six children in their Brooklyn home. Thomas was convicted of manslaughter and cleared of murder. He was released from prison after 32 years. Mass shootings in America Edmond post office shooting – 1986 Patrick Sherrill, a postal worker at the Edmond post office in Oklahoma, killed 14 co-workers and injured 6 others, before he shot himself. Oklahoma Highway Patrol Collection

“I come to offer the love and prayers of a nation. I am very mindful that mere words cannot match the depths of your sorrow, nor can they heal your wounded hearts,” he said

“I can only hope it helps for you to know that you’re not alone in your grief; that our world too has been torn apart; that all across this land of ours, we have wept with you, we’ve pulled our children tight. And you must know that whatever measure of comfort we can provide, we will provide.”

The shooting has also become the subject of wild conspiracy theories, not the least those espoused Alex Jones, host of Infowars, who claimed the massacre never happened.

In 2017, Megyn Kelly was criticised for giving time on her NBC show to let him double down on his opinions.

“When you say parents faked their children’s deaths, people get upset,” she said. He replied: “But they don’t get angry about half a million dead Iraqis killed by sanctions.”

Conspiracy theorist Alex Jones addresses his thoughts on Sandy Hook shooting being a hoax

Connecticut’s highest court was divided in its decision on Thursday, ruling 4-3 to reinstate a wrongful-death lawsuit and overturn a lower court decision that said the lawsuit was prohibited by a 2005 federal law that shields gun manufacturers from liability in most cases when their products are used in crimes.

The plaintiffs include a survivor and relatives of nine people killed in the massacre, the Associated Press said. They have argued the AR-15-style rifle used in the incident is too dangerous for the public and Remington glorified the weapon in marketing it to young people.

Remington has denied wrongdoing and previously insisted it can’t be sued under the federal law.

The majority of the high court agreed with most of the lower court’s ruling and dismissed most of the lawsuit’s allegations, but allowed a wrongful marketing claim to proceed.

“The regulation of advertising that threatens the public’s health, safety and morals has long been considered a core exercise of the States’ police powers,” said justice Richard Palmer.

Joshua Koskoff, a lawyer for the plaintiffs, told the state Supreme Court during arguments in November 2017 the Bushmaster rifle and other AR-15-style rifles were designed as military killing machines and should never have been sold to the public.

“The families’ goal has always been to shed light on Remington’s calculated and profit-driven strategy to expand the AR-15 market and court high-risk users, all at the expense of Americans’ safety,” Mr Koskoff said.

“Today’s decision is a critical step towards achieving that goal.”

Remington, based in Madison, North Carolina, filed for bankruptcy reorganisation last year amid years of slumping sales and legal and financial pressure as a result of the Sandy Hook shooting.