Should Ones Prison Record Be Removed Once Time Has Been Served?

Going to prison is an experience that can follow one for ever, years after time has been served. But is it fair to judge someone based on mistakes in the past? What if they committed a murder, shouldn't people have a right to know? Should some crimes automatically be expunged, such as drug related offenses - especially now that marijuana is no longer an illegal drug?  Should the purpose of imprisonment be to punish or to reform? Can all people be reformed, even sex offenders? Would you want an ex convict to be able to get a job in your child's school?