A bail bond office. (Kathy Willens/AP)

ROUGHLY 1,200 inmates in Philadelphia’s jails, about a fifth of the city’s total, are behind bars because they don’t have the cash to make bail. Not because of the severity of their alleged crimes; not because they have been judged a risk to their community; and not because they’ve been deemed a flight risk or antagonized a judge. They sit in cells in the United States’ fifth- ­largest city because they’re broke.

That patently unfair practice penalizes the poor and, disproportionately, minorities. It is a disgrace to the U.S. criminal-justice system that is mirrored in most cities and states nationwide. In recent years, voters and politicians have started to rethink it. It’s about time.

Philadelphia’s district attorney, Larry Krasner, has ordered a new policy: Starting immediately, city prosecutors will no longer seek bail for defendants charged with some misdemeanors and nonviolent felonies. That will allow as many as 4,000 defendants annually, or about 10 percent of the city’s caseload, to await trial at liberty instead of in jail, Mr. Krasner said. They will include people charged with 25 generally nonviolent crimes, including forgery; identity theft; food stamp or welfare fraud; prostitution; shoplifting; trespassing; marijuana and paraphernalia possession; resisting arrest; driving under the influence of alcohol; and providing false ID to a police officer.

Philadelphia’s stance is in line with recent legislation in neighboring New Jersey , which all but eliminated cash bail a year ago; since then, the jail population there has fallen by 20 percent, which is expected to translate over time into savings for taxpayers and the state. New York City is studying similar moves. The District of Columbia, a pioneer, scrapped cash bail during the 1990s.

New Jersey’s experience is instructive. Instead of setting cash bail, the state’s judges review a scored assessment, prepared by a newly established Pretrial Services Program and based on metrics including a defendant’s likeliness of posing a danger to the public and of not showing up at court, and then decide whether to order detention or release. A defendant’s bank book is not considered.

Predictably, the bail-bond industry has fought against such reforms, focusing on instances where the system has failed to lock up defendants who turned out to be dangerous. Yet there is scant evidence to suggest that cash is a precondition of ensuring that people charged with relatively minor crimes return to court to face justice.

In the District, for instance, about 90 percent of defendants who are released pretrial are not arrested again before their cases are resolved; of those who do run afoul of the law again, very few are rearrested for violent crimes.

Defendants awaiting trial can be effectively monitored with conditions such as mandatory drug testing, regular in-person or telephone check-ins, or GPS-equipped ankle bracelets. The threat of incarceration if they violate those conditions has been effective in making the District’s system work, and Philadelphia officials say they are following that lead.

Elsewhere, sleepwalking judges and prosecutors retain cash bail systems simply because they’ve been around as long as anyone can remember. That’s not good enough, or fair enough, for America’s justice system.