Connecticut is expected to pass a package of gun control and other laws described by supporters as the most comprehensive in the US.
Spurred on by the Newtown school massacre, debate on the far-reaching legislation, negotiated by Democratic and Republican legislative leaders, was expected to last for hours.
Some of the measures would take effect immediately, including expansion of the state's assault weapons ban, background checks for all firearms sales, and a ban on the sale or purchase of ammunition magazines holding more than 10 rounds. The bill also addresses mental health and school security measures, including money to help improve security at schools.
Governor Dannel Malloy, a Democrat, has said he will sign the legislation into law, even though it would allow people to keep their high-capacity magazines so long as they are registered with the state by Januar 1, 2014.
"I think you can make an argument, a strong argument, this is the toughest law passed anywhere in the country," he said.
Gun rights advocates question whether the legislation would have done anything to stop Adam Lanza, the 20-year-old who blasted his way in to the Sandy Hook Elementary School in Newtown on December 24. He fired off 154 shots with an assault rifle as he killed 20 children and six staff. He had earlier killed his mother, Nancy, and later killed himself.
"If it (the legislation) did something to prevent this incident, where the fault lies with the individual and the mother, not with the legitimate gun owners in this state, then we could probably support something," said Robert Crook, executive director of the Coalition of Connecticut Sportsmen.