the county sheriff, tom dart, is getting a lot of the credit. prosecutor who's been elected and re-elected sheriff since 2006, dart, as you'll see, is unconventional. it was a cold day at cook county jail when we met tom dart. he has redefined the role of sheriff. he sees the job as not just keeping people in jail, but helping some of them get out. he says many behind bars shouldn't be there. >> sheriff tom dart: how are you guys doing? >> pretty good. >> stahl: several times a month, dart mingles with the men in the jail's minimum security division, all of whom have been charged with low level, non- violent crimes. >> dart: what's your charge? >> i had a violation of probation. i was on probation for driving while license revoked. >> stahl: dart says the jail, with a population today of about ground for the poor and mentally ill. what percent do you think here really shouldn't be here? >> dart: i would suggest, conservatively, that half of the people here in the jail shouldn't be here. that they don't-- >> stahl: half? >> dart: they don't pose a