Sen. John Cornyn recalls visiting a Texas prison where some inmates taking shop classes could not read tape measures. Cornyn, who was previously a district court judge and Texas Supreme Court justice, knows that prisons are trying to teach literacy and vocations, trying to cope with the mental illnesses of many inmates and trying to take prophylactic measures to prevent drug-related recidivism by persons imprisoned for drug offenses. “The criminal justice system,” he says, “has become by default a social services provider.”

It is not, however, equipped to perform so many functions. Cornyn is part of a bipartisan congressional group negotiating sentencing reform, one of many needed repairs of the criminal justice system. What justice requires, frugality encourages: Too many people are in prison for too long, and too often, at a financial cost disproportionate to the enhancement of public safety. Texas has used alternatives to imprisonment to save $3 billion while crime rates have declined.

UCLA’s Mark Kleiman says “the deterrent impact of a punishment depends only weakly on its severity, but strongly on its swiftness and certainty.” What Cornyn and others are negotiating are selective reductions in the severity of some mandatory minimum sentences — each reduction reviewed by a court — for nonviolent offenses. This would enable government to devote increased resources to coping with violent and repeat offenders.

Speaking of repeat offenders: Much crime is committed by individuals who have weak impulse control, and Congress manufactures criminal offenses for the same reason. It should stop promiscuously multiplying federal crimes. Unlimited government develops an unlimited appetite for intervening in society’s dynamics. The regulatory state has a rage to regulate, sometimes by creating new crimes. The Heritage Foundation’s Paul Larkin notes that more than 40 percent of federal criminal laws enacted since the Civil War have come since 1970, and between 2000 and 2007 Congress legislated more than 450 new crimes — more than one a week. Has there really been a sudden multiplication of behaviors meriting society’s severe disapproval? And Larkin notes that “if criminal charges approximate parking tickets in their ubiquity, we have deprived the criminal law of the moral force necessary for it to persuade people to respect and obey its commands.”

The federal prison population, which devours 25 percent of the Justice Department’s budget, has increased more than 300 percent in less than 30 years. Only 7 percent are convicted of violent crimes. Granted, a person in prison poses no threat to the community. The problem is that almost everyone who goes to prison is going to return to the community from which he or she came, and most will not have been improved by the experience of incarceration.

It is axiomatic that social science cannot tell us what to do but can measure the results of what we are doing. What we are not doing well is the supervision of persons released from incarceration. Hence what UCLA’s Kleiman calls the “crime-incarceration-crime cycle.” He says “more people are sent to prison each year for violating probation or parole conditions than as a result of conviction for new crimes.”

Old theories about the causes of crime need to be rethought. During the Great Depression, unemployment soared to 25 percent yet in many cities crime fell. Demographic factors? Crime rates often vary with the size of society’s cohort of young males: Crime declined considerably during World War II not just, or even primarily, because unemployment was negligible but because so many young males were in military discipline.

In 2010, one year after the Great Recession’s jobs destruction doubled the unemployment rate, the property crime rate fell and violent crime reached a 40-year low. Current high incarceration rates had something to do with that. But how much? The late James Q. Wilson, the most accomplished social scientist since World War II, accepted the estimate that increased incarceration explains “one- quarter or more of the crime decline.” Wilson also suggested an environmental factor: “For decades, doctors have known that children with lots of lead in their blood are much more likely to be aggressive, violent and delinquent.” Since the 1970s, lead has been removed from gasoline and paint for new homes, and “the amount of lead in Americans’ blood fell by four-fifths between 1975 and 1991.” Wilson cited a study that ascribed more than half the 1990s’ decline in crime to the reduction of gasoline lead. Clearly, sentencing reform is just one piece of a complex policy puzzle.

© 2016, Washington Post Writers Group