The United States contains just 5 percent of the world's population, yet its prisons house nearly a quarter of all the people incarcerated around the globe. We imprison our citizens at a greater rate than any other country; as a result, nearly 1 in every 100 Americans today is living behind bars. Since 1970, the U.S. prison population has increased by 700 percent, to 2.4 million people. In Maryland, the state's prison population has tripled to more than 22,000, at a cost of more than $783 million a year.

Yet, the huge sums we spend on prisons haven't necessarily made us safer. The exploding prison population is largely a result of tough-on-crime policies dating back to the 1970s, many of which were driven more by emotion than by evidence of effectiveness. In fact, crime rates actually increased over much of the succeeding decades, even as the number of prisoners swelled.

In recent years, a growing body of evidence has suggested that large numbers of low-level, nonviolent offenders currently serving time in state prisons could be released without endangering the public. With state budgets strained by the recession, Maryland urgently needs to explore reforming its criminal justice system, with the aim of reducing its over-reliance on incarceration and the extraordinary economic and social costs associated with it — costs that are neither justified by public safety concerns nor sustainable in an era when limited state resources are under tremendous pressure.

A report last week by the American Civil Liberties Union cited the experience of a number of states in which bipartisan criminal justice reforms have resulted in substantially reduced prison populations and costs. Between 1999 and 2009, New York cut the size of its prison population by 20 percent. Texas, which is known for its tough stance on crime, managed to stabilize its prison population growth in 2007. Since then, both states have enjoyed their lowest crimes rates in decades. Other states that have launched ongoing prison reform efforts include Kansas, Mississippi, South Carolina, Ohio and Kentucky.

What can Maryland do to emulate the progress other states have made toward reducing the numbers and cost of their prison populations? The problem requires a three-pronged approach that includes systemic reforms to the criminal justice apparatus as a whole; reforms that focus on reducing the number of people entering jails and prisons; and policy changes that increase the number of people exiting and staying out of prison.

One systemic driver of prison population growth, for example, is the use of mandatory minimum sentences. Each year in Maryland, about 100 people enter the prison system as a result of mandatory sentences averaging about seven years, at a cost to taxpayers of about $200,000 each. Many of these individuals were convicted of drug offenses, but under mandatory minimum sentencing rules, judges' hands are often tied when it comes to distinguishing degrees of guilt according to the type and amount of drugs involved. Allowing judges more discretion in meting out punishment could reduce the number and cost of such prisoners, but a bill aimed at giving judges that power failed to pass the General Assembly this year.

A major problem on the "front end" of the criminal system is that far too many people are arrested for minor, nonviolent nuisance crimes such as disorderly conduct, public drunkenness or possession of small amounts of marijuana. Many of these people could safely be charged with a civil offense rather than a criminal misdemeanor and released on their own recognizance.

Last year, Maryland arrested some 23,000 people for marijuana possession and another 13,000 people for trespass, a catch-all offense that police often employ to clear crowds or detain people suspected of committing other offenses. Most of these people in fact pose little danger to the public. But once they enter the criminal justice system and acquire a record that must be reported to schools and potential employers, they can easily fall victim to a vicious downward cycle that leads to more serious brushes with the law.

Reform efforts also need to focus on reducing bail requirements for low-level, nonviolent offenders awaiting trial, who can be supervised by the probation system at far less cost to the state than incarcerating them. In 2009, it cost an average of $33,000 to hold an offender in a pretrial detention facility, compared with a fraction of that amount for pretrial supervision. Texas saved $2 billion by moving low-level, nonviolent offenders from detention centers to pretrial supervision; a similar effort in Ohio projects savings of more than $1 billion over the next four years.

Maryland could also reduce its inmate population by introducing graduated sanctions for offenders guilty of technical violations of their probation or parole. Technical violations can include failing to meet with a probation officer or report a change of address. Under current law, such violations automatically result in re-imprisonment, and in 2010 there were some 4,000 cases of people violating parole.

Parole and probation violations are a huge driver of the growth in prison populations nationally. Maryland could significantly cut the number of people who re-enter the prison system for such violations by creating alternative sanctions, such as community service or loss of privileges, that do not require reincarceration.

None of these reforms calls on police or prosecutors to be soft on crime or fail to hold people responsible for serious offenses. There have been too many cases recently in which people who should never have been allowed back on the streets committed heinous crimes because they were able to game the system. (John A. Wagner, the man currently on trial in the killing of Johns Hopkins researcher Stephen Pitcairn, is a case in point.)

Rather, these measures are simply a recognition that a substantial proportion of people currently in prison are low-level, low-risk, nonviolent offenders who are unlikely to commit the kinds of serious crimes that most concern the public. The cost of keeping them behind bars outweighs any benefit that accrues to society from their continued incarceration.

Most serious crimes are committed by a relatively small number of violent, career offenders. That's what the criminal justice system should be focused on. There's no reason Maryland can't follow the example of other states that have successfully reformed their laws and drastically reduced the cost of maintaining large prison systems populated by thousands of people who don't really need to be there.