While many Americans are shocked by the reason resignation of CIA Director David Petraeus, when one looks beyond the immorality of his affair, the evidence that made the case against him is no different than the evidence that convicts ordinary citizens charged with violations of state and federal criminal laws.
Petraeus and his lover wrote emails to each other, but they did not send them. Instead, they saved the emails as drafts so as not to create internet footprints of the transmissions. This is a trick that has been used by terrorists for many years. In a recent high profile case in the Phoenix, Arizona area, the wife of Maricopa County Supervisor Fulton Brock was convicted of sexual conduct with a minor for having a long standing affair with a teenage boy. She and the boy would access a particular email account, draft email messages to each other, but not send them. Each would have access to the account to read the messages. They did this to set up times and locations where she could molest him.
But the technique is far from fool proof. Web based emails such as Gmail, Yahoo, and other mainstream providers keep activity logs which store the IP address which accessed the email account. Through subpoenas, federal and state prosecutors in Arizona and surrounding states have been able to prove who accessed a particular email account by back tracing the IP address against internet provider subscriber records.
This technique has been used in prosecuting all types of offenses, including:
While in the end, it does not appear that Petraeus violated any criminal laws, it brought a stellar career to an abrupt end.