Complex sentence: Until the raid, the Sheriff's department and the FBI had been investigating jointly, but the FBI was not truthful with Speziale's detectives because the FBI was notified of the raid and declined participation.
Split into simpler sentences: Until the raid, the Sheriff's department and the FBI had been investigating jointly. Although it was determined later the FBI was not truthful with Speziale's detectives because they were notified of the raid and declined participation.