He has identified killers by studying ransom notes, emails, letters, and police interviews to spot secret confessions. He decoded O.J.'s "suicide note" to confirm he had committed a double murder. He deciphered the JonBenet ransom note to identify the child's killer. He decrypted letters from BTK to predict that he was about to kill again-the only profiler to do so. He studied statements by Joran van der Sloot and Deepak Kalpoe to tie them to the...