Hundreds of convicted murderers in Florida will likely get a chance to convince a judge that their life prison terms should be reduced because they were juveniles when they killed.

A U.S. Supreme Court decision Monday in two cases, Miller v. Alabama and Jackson v. Arkansas, struck down laws in 28 states that mete out mandatory life sentences without the possibility of parole for minors convicted of homicide.

The ruling, hailed by civil-rights activists, doesn’t mean Florida judges can’t still impose a life sentence on youths for first-degree murder — but they must now at least consider a defendant’s age.

“Kids are different. They are very impulsive. They follow other people. They don’t have a full understanding of the consequences of what they’re doing,” said Miami-Dade Assistant Public Defender Stephen Harper, who has worked on the issue and estimates some 225 Florida convicts could get new sentences. “The court found it is important for a judge to consider all these factors.”

Monday’s opinion follows the high court’s 2010 decision, based on a Jacksonville case, that ruled that sentencing minors to life without the possibility of parole in non-homicide cases constituted “cruel and unusual punishment.”

The teen in that case, Terrance Graham, received probation for a robbery, but was later arrested for another armed robbery and sentenced to life in prison for violating probation.

In most states, the Graham ruling meant simply amending a life sentence to include the possibility of parole. But Florida lawmakers abolished parole in 1983, and with 115 defendants affected, the state was in a bind. Many of those 115 defendants have since been re-sentenced, and some have been released from custody.

Monday’s high court decision drew heavily on the reasoning in Graham.

The first case involved Kuntrell Jackson, who as a 14-year-old in 1999 participated in the robbery of an Arkansas video store in which a clerk was shot and killed. Jackson did not fire the weapon, but was convicted of felony murder for participating in an armed robbery that led to a death.

The second case involved Evan Miller, who in 2003 beat an Alabama man to death with a baseball bat. Miller, 14 at the time, had been in and out of foster care because of his tumultuous family life.

Both teens — who under an earlier Supreme Court ruling are not eligible for the death penalty — were charged as adults.

Justice Elena Kagan, in the majority opinion, noted that Miller “deserved severe punishment” but that the automatic life sentence did not allow a judge to consider his troubled past.

The law “prevents taking into account the family and home environment that surrounds him — and from which he cannot usually extricate himself — no matter how brutal or dysfunctional,” Kagan wrote.

The justices who formed the majority were Kagan, Sonia Sotomayor, Ruth Bader Ginsburg, Stephen Breyer and Anthony Kennedy. The dissenters: Samuel Alito Jr., John Roberts, Clarence Thomas and Antonin Scalia.

The American Civil Liberties Union hailed Monday’s ruling.

“Today’s decision helps to restore some rationality to the treatment of juveniles in our criminal justice system,” said Steven R. Shapiro, ACLU national legal director. “Surely, it is not too much to expect that judges will at least consider the fact that a 14-year-old is standing before them when deciding whether to impose a sentence of life imprisonment without the possibility of parole, even in murder cases.”