The Crown says it will be seeking an adult sentence in the case of a 15-year-old boy charged in the killing of a York Regional Police officer.

The boy was remanded in custody during a court hearing that was conducted via telephone Thursday.

Charged with first-degree murder, the boy didn't attend the courtroom in Newmarket because he remains in hospital with serious injuries.

His lawyer sat with him in hospital, speaking to the court on behalf of his client through the speakerphone.

The boy is unable to speak, but he can hear, his lawyer said.

During the hearing, Crown attorney Peter Westgate informed the boy that the prosecution would be seeking an adult sentence if he is convicted of first-degree murder.

The case was put over to Sept. 15.

Sources told CTV News the boy is paralyzed from the neck down as a result of a single-rollover crash that killed York Regional Police Const. Garrett Styles on June 28.

Styles was dragged and pinned by a minivan during a traffic stop on Highway 48 in East Gwillimbury, north of Toronto.