States such as New Jersey, Arizona, and California have all recently adopted new rules eliminating or sharply curtailing the use of cash bail.

The New York government could pass its own bill as soon as this spring.Advocates for criminal justice reform say that ending the bail system would help curb mass incarceration.

Abolishing bail, however, raises the question of whether additional measures to detain criminal defendants will be needed. In a news conference last week, Mayor Bill de Blasio said the criminal justice system needs not only “reform” but also “tightening up,” particularly through allowing judges to consider a defendant’s level of “dangerousness” before granting bail.

In response, a dozen advocacy groups, such as the Legal Aid Society, released a statement accusing the mayor of attempting to “derail essential reforms to New York’s bail and parole release systems and to reverse progress made toward the decarceration of New York’s jails and prisons.”

How bail works

After they are arrested, criminal defendants ordinarily see a judge within 24 hours. Judges have a number of choices for determining what happens next.

The most lenient option is releasing defendants with a promise to return for their trial. The severest is ordering defendants, if they are deemed a flight risk, to be detained in jail until a trial verdict or plea deal.

Bail provides a middle path: Defendants remain free but face the threat of a financial penalty.

Setting bail

New York judges can choose from nine different types of bail, some of which require no upfront payment. Typically, however, judges favor cash bail, which calls for immediate payment to the court. If the court’s requirements are met, the bail money is returned to whoever put it up.

Judges weigh a variety of factors, including the financial resources of the accused and the recommendation of prosecutors.

Wealthy defendants can afford to pay the amount directly — Harvey Weinstein, for instance, had his lawyer hand over a cashier’s check worth $1 million during his arraignment.

The role of the bondsman

Those who cannot afford bail must choose between jail and reliance on a commercial bail bondsman. Under New York law, bondsmen can charge a fee of up to 10 percent for bail set under $3,000 and only 6 percent for any amount above $10,000.

The bondsman keeps this payment regardless of the outcome of the case. This compensates for the risk taken by sponsoring an accused criminal — since if that person doesn’t show up to court, the bondsman must fork over his or her bail to the government.

The problem with bail

The most fundamental criticism of the bail system is that it needlessly imprisons poor people. In 2010, when he was 16, Kalief Browder was accused of stealing a backpack and released on $3,000 bail, which his family could not afford. Browder spent nearly three years in jail on Rikers Island waiting for trial before the charges against him were dismissed. In 2015, he committed suicide.

“Whether you’re in jail for three days, three weeks, three months or three years, it’s an accelerator of human misery,” said Jonathan Lippman, the former chief judge of New York state’s highest court and currently the chairman of an independent commission on criminal justice reform. “You come out a changed human being.”

The bondsman business

New York bondsmen are more tightly regulated than those in other states, but they have been accused of failing to return collateral and charging illegal fees to their generally poor clientele. Last year, the Department of Consumer Affairs accused the bondsman Marvin Morgan of circumventing industry rules. For one thing, he charged up to $1,000 for courier costs. Morgan lost his bondsman license.

Eduardo Guilarte, founder of BailNYC on Baxter Street, said that criticisms of the bail bond industry are a “smokescreen” for deeper social issues, and that bondsmen fulfill a unique duty at no cost to taxpayers.

“For the system to work, it has to matter to somebody,” Guilarte said. “When a defendant doesn’t show up, it matters to me, because I have to write that check right then and there.” No one will have such an incentive to find accused criminals skipping court if reform measures eliminate bondsmen, he argued.

Changing the law

Politicians used to back Guilarte’s views. Just last year, the Republican-controlled New York state Senate declined to move a measure passed by Democrats in the Assembly to do away with cash bail for many crimes.

But Democrats now control the Senate. The new deputy majority leader, Michael Gianaris, has sponsored a bill that would eliminate cash bail. Gov. Andrew Cuomo, a Democrat, says eliminating cash bail is one of his top priorities.

“I’ve never seen this much momentum, which leaves me very optimistic,” Gianaris said. He added that eliminating bail could be part of a criminal-justice-reform package to be passed along with the state budget by March 31. “But on this issue more than most, it’s critical that we do it right.”

So bail is abolished. Then what?

The California government recently passed a law replacing cash bail with a new system, known as risk assessment, which has divided advocates of reform.

The new law creates levels of risk based on likelihood to show up in court and threat to the public, with some defendants guaranteed time in jail before their case is decided. Since these judgments are based on criminal history, and the criminal justice system has been riddled with bias, “risk assessments are inherently bringing forward that racism and that discrimination,” said Tina Luongo, chief criminal defender of the Legal Aid Society. She compared this to de Blasio’s suggestion about judges determining “dangerousness.”

Alternatives to bail

In March 2016, New York implemented a citywide program called supervised release. It resembles parole: in lieu of jailing people who cannot post bail, a judge can let them go free on the condition that they agree to meet with a social worker one to four times a month and maintain regular phone contact with that person until the outcome of their case.

Other initiatives that sidestep bail include problem-solving courts and diversion programs. They replace fines and jail with programs that help defendants, such as drug treatment, and mandatory community service.

Bail would also become less of a problem if judges simply used alternatives to cash bail already on the books, Luongo explained. For instance, judges can make bail conditional on defendants first missing a court date.

Asked if meaningful change could happen within the system as it stands, Luongo replied, “Yes. Tomorrow.”