As lawmakers consider loosening life sentences for juvenile criminals, a new report released Wednesday said more than 300 California inmates are locked up for life after committing crimes when they were younger than 18.

That’s nearly 12% of all 2,570 inmates who were juveniles when they were sentenced to life without parole.

“California’s use of this sentence remains particularly troubling,” said the report, which was released by Human Rights Watch.

Although sentences of life without parole are limited to homicide cases, the report said nearly half of the juveniles did not commit the actual murder.

Elizabeth Calvin of Human Rights Watch, the report’s author, said the harsh sentences are the wrong approach.

“No one can predict who a teen will be at age 40,” she said in a statement. “When California sentences a 16-year-old to die in prison, the state ignores what science, parents and teachers have long known: young people have tremendous potential to change, grow and mature.”

[Updated at 2:55 p.m. The report said there are 301 state inmates who were sentenced to life without parole for crimes committed when they were less than 18 years old. The California Department of Corrections and Rehabilitation pegged the number at 309 inmates.]

The state Senate approved a bill that would allow juveniles to petition for parole if they are sentenced to life. The Assembly rejected the proposal, but is expected to consider it again soon. Families of victims have fought efforts to allow juvenile killers to seek parole.

The U.S. Supreme Court is also considering whether sentencing juveniles to life in prison constitutes cruel and unusual punishment. Justices will hear oral arguments March 20.

-- Chris Megerian

Twitter: @chrismegerian

RELATED

Juvenile prison system needs reform, lawyers say

Supreme Court to weigh juveniles' life sentences without parole

Young killers serving life without parole may get chance at freedom

Photo: A juvenile inmate being held in a waiting cell, before a meeting with someone. Credit: Los Angeles Times