Many attorneys need to track down people who may be incarcerated. There are several sites that will provide information on criminal history that can help a researcher verify whether someone was incarcerated and if so, for what offense.
Mugshots.com is a website primarily devoted to displaying mugshots of celebrities, individuals who have committed outrageous acts, and those whose appearance is unusual. If you need to find the mugshot of someone who has been in the news lately, this can be worth a look.
VINELink is the Victim Information and Notification Everyday network, which "allows crime victims to obtain timely and reliable information about criminal cases and the custody status of offenders 24 hours a day."