A new study just released by researchers from Carnegie Mellon University has attempted to devise a model to quantify the relevance of a criminal record for employment on the basis that the importance of a past criminal record recedes over time when a person is not re-arrested. The study looks to develop a methodology to measure how much time must pass before an applicant with a criminal record is no greater risk than an applicant without a criminal record. (Blumstein, Nakamura, “Redemption in the Presence of Widespread Criminal Background Checks,” Criminology, Volume 47, Number 2 (2009)).
The study, based upon limited data just from the state of New York, found that with time, a person with a criminal record was no greater threat than persons without a criminal record. It suggested that depending upon the offenses included in the study and the age at which the offenses were committed, that after approximately 4½ to 8 years without further arrests, an offender had a minimal risk of re-offending. Of course, the more violent the offense, the longer the time would be required before a person could be considered “redeemed.” Serious crimes such as murder, rape, or child molestation were not part of this particular study, but presumably more serious crimes would have a different result. 
Although there is a temptation for the press to take “sound bites” from the findings, it is abundantly clear from the authors of the study themselves that this is only a beginning. The authors were clear that much more study was needed and that there are substantial issues still to be addressed. The author’s characterization that the study represents a “significant step forward in area where so little is known empirically” is well-taken. 
The study does not have nearly enough data to reach conclusions from which policy recommendations can be effectively made, has not been reviewed critically by other professionals, and most importantly has a number of drawbacks that can affect its reliability. Many of these limitations were acknowledged by the authors.  There are also unstated assumptions in eh study that would certainly skew any results. 
For a more in-depth analysis of why this study cannot be the basis to make policy changes, see a more complete analysis by ESR at: http://www.esrcheck.com/Blumstein-and-Nakamura-study-on-redemption-in-Criminology.php.