BOSTON – The conviction of Phillip Chism for the brutal rape and murder of his high school math teacher has rekindled a debate over parole for teen killers, and renewed calls for lawmakers to toughen prison sentences.

Chism was found guilty of first-degree murder by an Essex County jury on Wednesday in the 2013 slaying of Danvers High School algebra teacher Colleen Ritzer. Prosecutors say Chism followed Ritzer, 24, into a school bathroom, strangled her, stabbed her at least 16 times with a box cutter, raped her, and then dumped her body in the woods near the school.

Chism, now 16, was tried as an adult but will still be eligible for parole in 13 to 23 years, depending upon the sentence he receives in January. He has already spent nearly two years in jail while awaiting trial.

As a juvenile, he cannot receive a sentence of life without parole, following recent decisions by the U.S. Supreme Court and the Supreme Judicial Court of Massachusetts. Both ruled that teen killers should be given a chance at parole.

Adults convicted of first-degree murder in Massachusetts automatically receive sentences of life without parole.

“The reality that families like mine and the Ritzers might have to face parole hearings is devastating,” said Sean Aylward, brother of Beth Brodie, a 16-year-old Pentucket Regional High School cheerleader who was beaten to death in 1992.

Aylward said he and family members of other victims want lawmakers to revisit the issue and act to keep teen killers behind bars.

In 2014, Sens. Bruce Tarr, R-Gloucester, and Barry Finegold, D-Andover, filed a proposal backed by more than a dozen other lawmakers that would require a juvenile convicted of first-degree murder to serve at least 35 years in prison before becoming eligible for parole. Their law applied retroactively to convicted murderers.

The bill was changed before it was approved by the Legislature and signed by Gov. Deval Patrick.

Under the new sentencing guidelines, juveniles convicted of first-degree murder are eligible for parole after serving 20 to 30 years in prison, depending upon the circumstances.

Because the Legislature changed the law after Chism murdered Ritzer, he will be sentenced under the guidelines outlined by the state’s high court, which make him parole-eligible after serving 15 to 25 years.

“I think we have an obligation to revisit this issue, to make sure that public safety is protected,” Tarr said Thursday. “Clearly this legislation put us in a better position than we would have been with the high court’s decision, but there’s still a lot more work to be done.”

Rep. Ted Speliotis, D-Danvers, who co-sponsored the bill setting a 35-year minimum sentence for teen killers, said the Chism case has brought the issue back to the forefront. He wants the Legislature take it up again.

“It really hits you in the gut when you think this person could be eligible for parole in his early 30s,” Speliotis said. “We simply can’t allow people like this, who have taken a life so cruelly and so callously, to go back into society.”

Rep. Brad Hill, R-Ipswich, another sponsor of the original bill, agrees that the sentencing guidelines for teen killers are too lenient.

“It’s absolutely something we should be taking a look at again,” he said. “We need to do whatever we can to make sure that someone who commits a crime like this is put behind bars for a long as is constitutionally allowed.”

Aylward said advocates are pushing to change the state Constitution to require mandatory life sentences for teen killers. The change would need approval in two consecutive sessions of the Legislature before being put to voters in a statewide referendum — a process that could take three years or more.

“There are a number of legislators who have said they are willing to get on board with this, but it’s been hard to get the ball rolling,” he said. “Nobody wants to commit to the task because it’s going to take two sessions to get it done.”

In 2012, the U.S. Supreme Court struck down mandatory life sentences for juveniles convicted of first-degree murder as a violation of the Constitution’s protection against “cruel and unusual punishment.” The state Supreme Judicial Court followed with a similar ruling in December 2013.

The state’s high court — ruling in the case of Gregory Diatchenko, who was 17 when he stabbed a man as he sat in a car in Boston’s Kenmore Square in 1981 — held that sentences of life without parole fail to account for a young defendant’s likelihood of rehabilitation.

Prior to those rulings, Massachusetts boasted some of the country’s toughest laws for juveniles convicted of first-degree murder.

A 1996 law mandated that juveniles 14 years and older charged with murder be tried as adults. Those found guilty faced life in prison – the mandatory sentence for first-degree murder.

Chism will be held at a juvenile detention center in Worcester until he’s 18, then will be moved to a state prison. He could be up for parole as early as his 29th birthday, if a judge determines that he should be eligible after serving 15 years.

The teen was also found guilty of felony aggravated rape and armed robbery, for which he faces sentences of up to life in prison, with the possibility of parole. The judge could order Chism to serve his sentences consecutively or concurrently, which will affect his parole eligibility.

Tarr said his legislation also required the state to develop an evaluation for juveniles convicted of first-degree murder, to determine if they should be eligible for parole.

“If we’re going to give juvenile offenders an exemption based on immaturity or that they lacked the mental capacity when the committed crime, they should have to prove that,” he said. “It shouldn’t be just presumed.”

Christian Wade covers the Massachusetts Statehouse for CNHI’s newspapers and websites. Reach him at cwade@cnhi.com.