Adrian "A.J." Gonzalez, who was 15 when his 8-year-old neighbor Madyson "Maddy" Middleton disappeared in the summer of 2015 in Santa Cruz, had long ago confessed that he killed her. But he's remained in legal limbo because of his age at the time of the crime, and now, at age 21, he has pleaded guilty and will finally be sentenced.

The Bay Area was riveted to the case of Middleton's disappearance in July 2015, which also garnered national attention when, within a day, police found her body stuffed in a recycling bin in the complex where she lived. Police quickly homed in on Gonzalez, the girl's teenage neighbor, who was seen on surveillance video attempting to dispose of the body just downstairs from where he lived with his family in the Tannery Arts Complex.

He was alleged to have lured the girl to his apartment on the third floor with the promise of ice cream, bound her with duct tape, and raped and strangled her.

Gonzalez would ultimately be charged with sexual assault, kidnapping, murder, sexual penetration by a foreign object, and two counts of forcible lewd acts on a child. He first entered a plea of not guilty on all charges in September 2015. And ever since, he has been in juvenile detention, though California has oscillated between wanting to try him as an adult and wanting to try him as a juvenile.

A nine-week transfer hearing in 2017 resulted in a judge ruling that Gonzalez should be tried as an adult and housed in an adult prison, but defense attorney Larry Biggam appealed that ruling.

At the time, Biggam said, "It’s a serious crime, let’s be clear about that. But I think this kid is not so depraved and incorrigible that we just need to throw him in adult court."

California passed SB-1391 in 2018, which bars defendants 15 years old and younger from being transferred to adult court, and in February, the California Supreme Court unanimously upheld the law. That decision stemmed from a case in Ventura County in which a 15-year-old was charged with two counts of murder. The ruling affirmed that prevailing psychological research has found that the brains of children under the age of 16 have not fully developed, and they can not be found culpable for the actions in the same manner as adults.

As KRON4 reports, Gonzalez entered his guilty plea on Tuesday, and Biggam immediately pointed to the state Supreme Court's decision for vindicating his position from the beginning.

"The issue in this case has always been this: will Adrian receive treatment and rehabilitation services in an age-appropriate facility or receive pure punishment in an adult prison," Biggam said in a statement. "The Supreme Court recently resolved that issue when, in a 7-0 decision, they upheld SB1391 which bans the transfer of 14 and 15-year-old kids to adult courts. It is, in my view, good public policy and promotes public safety. Kids tried and punished in adult courts re-offend sooner, more often, and for more serious crimes than those kept in the juvenile justice system. A meaningful opportunity for reform requires a correctional setting which treats and does not further traumatize its occupants. Although no correctional institutional is perfect, Adrian will have a better chance at growth, change, and maturation at the Department of Juvenile Justice compared to San Quentin or Soledad."

Juvenile defendants are rarely held past their 25th birthday, and the Santa Cruz County District Attorney confirmed that Gonzalez is likely only going to be held another four years for his crimes.

Previously: Teen Who Admitted To Rape And Murder Of Santa Cruz 8-Year-Old To Be Jailed With Adults