Answer
The answer is 10. Dennis Rader, also known as BTK (Bind, Torture, Kill), confessed to murdering 10 people in Wichita, Kansas, between 1974 and 1991. He would taunt the police and send letters describing his crimes to the media, using codes and puzzles. After decades of evading capture, he was eventually caught in 2005 through DNA evidence and sentenced to 10 consecutive life sentences.