(CNN) -- The Connecticut Senate on Thursday voted to repeal the death penalty, setting the stage for Connecticut to join several states that have recently abolished capital punishment.
In the last five years, New Jersey, New Mexico, New York and Illinois have repealed the death penalty. California voters will decide the issue in November.
The bill now goes to the House of Representatives, where it is also expected to pass. Gov. Dannel Malloy, a Democrat, has vowed to sign the measure into law should it reach his desk, his office said.
"For everyone, it's a vote of conscience," said Senate President Donald Williams Jr., a Democrat who says he's long supported a repeal. "We have a majority of legislators in Connecticut in favor of this so that the energies of our criminal justice system can be focused in a more appropriate manner."
In 2009, state lawmakers in both houses tried to pass a similar bill, but were ultimately blocked by then-Gov. Jodi Rell, a Republican.
Capital punishment has existed in Connecticut since its colonial days. But the state was forced to review its death penalty laws beginning in 1972 when a Supreme Court decision required greater consistency in its application. A moratorium was then imposed until a 1976 court decision upheld the constitutionality of capital punishment.
Since then, Connecticut juries have handed down 15 death sentences. Of those, only one person has actually been executed, according to the Death Penalty Information Center, a nonpartisan group that studies death penalty laws.
Michael Ross, a convicted serial killer, was put to death by lethal injection in 2005 after giving up his appeals.
"It's not a question of whether it's morally wrong, it's just that it isn't working," said Richard Dieter, the group's executive director. "I think when you hear of 15 to 20 years of uncertain appeals, that's not closure and that's not justice. It's a slow, grinding process."
Eleven people are currently on death row in Connecticut, including Steven Hayes and Joshua Komisarjevsky, who both were sentenced for their roles in the 2007 murders of the Petit family in Cheshire, Connecticut.
The high-profile case drew national attention and sparked conversations about home security and capital punishment. In vetoing the measure to eliminate the death penalty in 2009, Rell cited the Cheshire deaths.
Dr. William Petit, the sole survivor in that attack, has remained a staunch critic of repeal efforts.
"We believe in the death penalty because we believe it is really the only true, just punishment for certain heinous and depraved murders," Petit told CNN affiliate WFSB.
Advocates of the existing law say capital punishment can act as a criminal deterrent and provides justice for victims.
Opponents say capital punishment is often applied inconsistently, can be discriminatory and has not proven to be an effective deterrent. They also point to instances in which wrongful convictions have been overturned with new investigative methods, including forensic testing.
"Mistakes can be made and you may not know about it until science later exposes them," said Dieter.
But a recent Quinnipiac poll found that 62% of Connecticut residents think abolishing the death penalty is "a bad idea."
"No doubt the gruesome Cheshire murders still affect public opinion regarding convicts on death row," said Quinnipiac University Poll Director Douglas Schwartz.
That number jumps to 66% among Connecticut men, and drops to 58% among the state's women, according to the poll.
The Senate's proposed law is prospective in nature, meaning that it would not apply to those already sentenced to death.
Read more about this story from CNN affiliate WFSB.