A Tucson teenager originally charged as an adult with attempted murder of his adoptive father has been transferred into the juvenile system.

Pima County Superior Court Judge Deborah Bernini ruled Wednesday that the 15-year-old would be better off in the juvenile system because of mental-health services not available in the adult system.

The boy was 14 last October when Pima County sheriff's officials said he and his then-17-year-old girlfriend, Angela Swink, decided to run away together after killing his adoptive parents. Swink is scheduled to enter a plea agreement today. The adoptive parents were in the process of terminating their parental rights, and the teen was living in foster care.

Officials said the boy attacked the dad from behind, choked him and tried to cut his throat. The dad overcame the boy and called 911.

In her ruling, Bernini noted the father didn't require medical treatment and the mom wasn't home. The father grabbed the knife from the teen, put away his groceries and offered both teens ice cream, Bernini wrote. He called 911 from a convenience store and waited with the pair for deputies.

The boy was removed from his teenage mother while he was a baby and lived in seven foster homes before his adoptive parents took him in, Bernini noted.

The couple, who were 57 and 70 when they adopted the teen, home-schooled him until he was 12, and he failed his first year of public school.

The teen has been arrested for assaulting the mother, but "both incidents involve documented physical assaults committed against him by (the adoptive mother)," Bernini said.

"The records are replete with documented physical and mental abuse of the defendant at the hands of his adoptive parents," Bernini wrote. She also noted he'd been hospitalized twice for suicidal thoughts.

After the teen was placed back in foster care and a special-education class, "his behavior showed dramatic improvement," Bernini said. She said police records indicate Swink was the instigator.

By transferring the teen into the juvenile system, his dependency and criminal cases can be handled by the same judge.

On StarNet: Follow the news and events at Pima County's courthouses in Kim Smith's blog, At the Courthouse, at azstarnet.com/courthouse

Contact reporter Kim Smith at 573-4241 or kimsmith@azstarnet.com