Massachusetts’ highest court ruled in two separate opinions that “emerging adults” must be offered at least the possibility of parole when sentenced to life in prison — a decision that could free many more people than just the two plaintiffs.

In the cases Commonwealth v. Mattis and Commonwealth v. Robinson, the Supreme Judicial Court ruled Thursday that those they term an “emerging adult,” which Chief Justice Kimberly S. Budd defined as those 18 through 20 years old in her 37-page majority opinion in Mattis, could not be sentenced to life without the possibility of parole.

Supreme Judicial Court Chief Justice Kimberly Budd speaks in 2020. (Staff Photo By Stuart Cahill/MediaNews Group/Boston Herald)

The opinion is based on the 2012 U.S. Supreme Court case Miller v. Alabama and the SJC’s own ruling the following year in Diatchenko v. District Attorney for the Suffolk District, which struck down such a sentence for juveniles. It is also based on “updated research on the brains of emerging adults,” according to the opinion, which has “confirmed what many know well through experience: the brains of emerging adults are not fully mature.”

“Here, we consider whether our holding … should be extended to apply to emerging adults,” Budd wrote in Mattis. “Based on precedent and contemporary standards of decency in the Commonwealth and elsewhere, we conclude that the answer is yes.”

The ruling is to be applied not just in the cases of the appellees — convicted murderers Sheldon Mattis, who was 18 when he was involved in the murder of Jaivon Blake in 2011, and Jason Robinson, who was 19 when he murdered Inaam Yazbek in 2000 — but to all cases retroactively.

The Suffolk District Attorney’s office on Thursday announced that it had identified about 70 inmates who will now eventually be eligible for parole based on the SJC decisions. The ruling does not immediately grant them parole, the DA cautioned, but makes them eligible under the state Parole Board’s standards.

“We know this decision will generate questions among the survivors of homicide victims of both the immediate and distant past, and we want to make sure that those survivors get accurate information about the ruling,” Suffolk DA Kevin Hayden said. “Our victim witness advocates will help these families and loved ones understand how the SJC decision affects them.”

“I’m urging anyone impacted by this decision to contact us so we can provide the information necessary to understand what this ruling does and does not do,” he added, directing those concerned to his office’s website, at SuffolkDistrictAttorney.com, for more information.