OKLAHOMA CITY - Three people have taken the stand in a hearing to determine if 13-year-old Crystian Rivera will be tried as a juvenile or as an adult for the murder of his baby sister.

Rivera appeared in Oklahoma County District Court Friday.

Court records reveal Rivera told investigators he shook his sister after she interrupted a video game he was playing. She later died in the hospital.

Both Rivera's mother and step father were in the courtroom for today's hearing.

So were a couple of neighbors and friends.

Rivera's mother and stepfather are also facing charges of child neglect in the death of the nine-month-old baby girl. But Crystian is facing the very adult charge of murder. And though he has been charged as an adult, his attorneys are trying to have him tried as a youthful offender, because of his young age.

Rivera arrived to court wearing the red jail clothes all juveniles wear to differentiate them from the adult prisoners. He also appeared to be smiling as he was led into the courtroom. The first witness to take the stand was Rivera's 5th grade teacher who said he was a mild-mannered, soft-spoken, respectful student who was easy to get along with and got good grades.

"He was a good kid," said Debbie Bounds, Rivera's 5th grade teacher, who testified she had no behavioral issues with him.

A former neighbor also testified.

"He was just the kid you wish all the kids could be like," said Barbara Williams, who used to live across the street from the Rivera's old home.

"I have never seen Crystian angry ever."