Eagle resident Andrew Cassell is suspected of causing a crash on Highway 44 near Horseshoe Bend Road Halloween night. His passenger, Aldina Ekic, 21 of Boise, died at the scene.
Cassell entered the not guilty plea Monday in Ada County court.
Prosecutors say Cassell's blood alcohol content registered a .14 after the crash. He also, they say, admitted to drinking and had a bar wristband on his wrist at the time of the crash.
Troopers say costume material was found in the car and say the two may have been coming from a Halloween party.
Cassell's trial is scheduled for April 8.