Dennis Rader is a serial killer who began murdering in the Wichita, KS area in 1974 and continued until 1991. Unlike most murderers, he would take a number of years between his crimes, and the last hiatus he had lasted for close to 15 years. In fact, it lasted until the law finally caught him. Rader was supposedly in the planning stages of another murder at that time. Some also believe that there may have been more murders during his supposed hiatus, but evidence has yet to surface.
Rader was a killer who enjoyed taunting and toying with the police and this would eventually be what undid him. He had the moniker BTK, which stands for Bind, Torture, Kill, and his narcissism caused him to reach out to the police and send letters to the media. He stopped communicating with them during the hiatus, but resumed in 2004, when he told the media that he was planning to start murdering again. He began communicating with Lt. Landwehr, head of the task force trying to catch BTK. Rader asked the lieutenant if it would be ok to communicate via floppy disk rather than a traditional letter. The police said that yes, it would be fine.
Anyone versed in computer forensics can probably guess what happened next. Rader sent the floppy to a local television station, and the police were able to trace the floppy to the computer that he used in his church. They were able to bring Rader in just days later, all thanks to the hard work of the task force trying to find him and the forensics experts who were able to trace the disk.
This is one of the most sensational cases where digital forensics helped to save the day. As crime grows and takes over the web, you can be sure there will be many more instances of criminals getting their comeuppance thanks to computer forensics.