Accused Anthrax Killer Aided Agents

So if Army scientist Bruce Ivins had a history of mental problems and access to anthrax, why did it take so long for him to become a suspect in the anthrax killings of 2001?

The New York Times provides at least a partial answer today: Because at the beginning of the investigation, Ivins was nothing but helpful to FBI investigators working the case. He even served as a Red Cross volunteer when the FBI searched a pond near Frederick, Md., in 2002 for clues related to Stephen Hatfill, who was then the leading suspect in the case. Ivins served coffee, doughnuts and chocolate bars to agents before they realized where he worked and told him to leave before he compromised the investigation.