Spokane, Wash. -

Alleged pipe bomber Kevin Harpham will not use an alibi defense in his federal weapons of mass destruction trial.

His father, Cecil Harpham, told KXLY in March his son was with him in Kettle Falls the day the bomb was planted in downtown Spokane.

A federal Court Judge ordered Harpham's attorneys to file documents notifying prosecutors they intended on using a alibi defense and they did not.

It's unclear what defense strategy they will now use. Phone calls by KXLY TV reporters to federal defenders were not returned today for clarification.

Harpham faces Federal weapons of mass destruction charges for allegedly planting a pipe bomb January 17, 2011 on the corner of Washington and Main.

It was hidden in a backpack along the route of the annual Martin Luther King, Jr. Day Unity March. Authorities found the device before it detonated. The FBI said the explosive device had the potential of causing multiple casualties.

The trial is set to start at the end of August.