If society is going to take criminals off the street, it can either do so indiscriminately by raising penalties across the board, or it can impose longer sentences on those it believes most likely to commit further crimes if released. Both justice and efficacy require focusing on career criminals. Research has long established that a fairly small percentage of criminals commit a disproportionate share of the crimes. Furthermore, there are moral and constitutional restraints on the factors that can be used in sentencing. Even if research were to find a correlation between growing up in a broken home and recidivism, for example, it would be obviously unjust to base a sentence on a factor beyond one's control.
Criminal record is the single most important factor in identifying the career criminal.
Common sense, backed up by research, indicates that felons with multiple convictions are more likely to commit new crimes upon release. It is a psychological truism that the best predictor of future behavior is past behavior. Not surprisingly, one of the best predictors of future criminal conduct is past criminal conduct, and the parole-prediction literature amply supports this fact. Enhancement for prior convictions is based on an objective, previously adjudicated fact, and it is based on the defendant's voluntary, antisocial choice to commit the prior crime. The predictive power of a criminal record to forecast future recidivism is obviously far from perfect.