Sgt. Michael Walker, an Army medic, plead not guilty in Honolulu on Thursday in the stabbing death of his wife. His former lover and alleged co-conspirator, Ailsa Jackson, also plead not guilty. Court documents indicate she will change her plea later this month: she appears to be cooperating with prosecutors.

A federal grand jury indicted Sergeant Michael Walker, an Army medic, on Wednesday in the fatal stabbing last year of his wife Catherine, the Associated Press reports. Walker is accused of conspiring with his lover to murder his wife and cover it up to look like a burglary.