The wave of bioterrorism that killed five people shortly after 9/11 is unsolved and largely forgotten, but it played a role in sending us off to war in Iraq, so it is of considerable historical importance in understanding how we got to where we are.
Feeling cocky after my recent run of investigative successes, I sat down last week to solve the anthrax case. A quick scan identified a character who many on the Internet had wondered why he, rather than the hapless Stephen Hatfill, hadn't been put through the ringer. He's a microbiologist, retired Army officer, worked at the Army base where they keep lots of anthrax, had been mean to an Arab colleague, was involved in lots of unseemly stuff, etc etc. The more I Googled, the more the pieces fell into place ... until, pffft, I looked at the evidence again from a different angle and it all blew away.
Sure, I could make the bits and pieces fit into the notion that he was the anthrax mailer, but then a simpler explanation occurred to me: He was just a jerk who had done some jerky things over the last 15 years. I'm not going to mention his name, but if you know who I'm talking about and think he did it, try to force yourself into a gestalt where you assume he didn't do it and see if you can think of less sinister explanations for the facts known about him.