FARGO, N.D. -- A North Dakota judge deferred from assigning to adult court a Sun Prairie teen accused of killing his 16-year-old sister until officials determine whether a psychiatric evaluation is necessary.

The delay means that it could take up to two months to find out if Sergei Carlson, 15, will face murder charges in adult court. Carlson made an appearance on Monday in juvenile court in Fargo, WISC-TV reported.

The teen is accused of killing Whitney Carlson while visiting his mother for the summer. The girl lived with her mother in Fargo, WISC-TV reported.

The siblings' uncle has said that while Sergei Carlson lived with his father in Wisconsin, he spent time with his mother in Fargo.