Holding a defendant in jail simply because they can’t afford a fixed bail amount is unconstitutional, the Justice Department said in a brief it filed Thursday in a Georgia lawsuit.

"Bail practices that incarcerate indigent individuals before trial solely because of their inability to pay for their release violate the Fourteenth Amendment," the department said in an amicus brief, referring to the Equal Protection Clause of the Constitution.

"Fixed bail schedules that allow for the pretrial release of only those who can play, without accounting for the ability to pay unlawfully discriminate based on indigence," said the department.

The friend-of-the-court brief marks the first time the Justice Department has submitted a legal opinion in a federal court on bail systems in state and local courts. It also is the most direct action by the Obama administration to push states to reform court practices it has said discriminates against poorer defendants. Those defendants tend to be black, Latino, or high school dropouts, as well as those with mental illness or substance abuse problems.

The Justice Department filed the brief with the 11th US Circuit Court of Appeals in the class-action lawsuit of Maurice Walker, a Georgia man who spent six days in jail in the city of Calhoun because he couldn’t pay the $160 bail amount for a misdemeanor charge.

Mr. Walker was arrested in September, and charged with a misdemeanor of walking while intoxicated. According to a Calhoun ordinance, the charge carried a preset bail of $160 for Walker to avoid jail before his first appearance before the judge. Walker – who said he lives on $540 a month in Social Security disability benefits – was unable to pay that amount. So, he remained in prison following his arrest while he waited for his first court appearance before a municipal judge.

Walker, in the class-action lawsuit, challenged the city’s bail policy. His attorneys argue the ordinance violates the equal protection rights of poor defendants, and should be suspended for any defendant that can’t “pay a generically set amount” of bail.

A US District Court judge sided with Walker in January. The judge suspended the policy until the case is settled, instead ordering those arrested on misdemeanor offenses be released on their own recognizance, according to NBC News.

Calhoun appealed the ruling to the 11th Circuit. In the appeal, attorneys for the city said defendants such as Walker “should not be relieved from the requirement of having to attempt to make bail merely upon a bare claim of indigent status.” They added misdemeanor and city ordinance violations for which defendants face preset bail “are not petty, trivial offenses,” and those arrested for violations do “pose a risk or danger to the community and, in some instances, themselves.”

This isn’t the first time the Justice Department has labeled preset bail amounts as unconstitutional. After an investigation into the police department in Ferguson, Mo., the Justice Department encouraged all states and local courts to abandon preset bail amounts. In a letter to all state chief justices and court administrators it sent out March 14, the department said preset bail discriminated against poorer defendants. The same day, the department announced the creation of a task force to will investigate fines, fees, and bail practices.

The Justice Department’s actions come as new evidence indicates many state and local court systems work against the poor. A yearlong investigation by NPR found that the post-arrest process in the criminal justice system appears to work against poorer defendants.

The costs of the criminal justice system in the United States are paid increasingly by the defendants and offenders. It's a practice that causes the poor to face harsher treatment than others who commit identical crimes and can afford to pay.

And defendants, NPR found in a state-by-state survey, are charged for many government services that were once free.

These fees – which can add up to hundreds or even thousands of dollars – get charged at every step of the system, from the courtroom, to jail, to probation. Defendants and offenders pay for their own arrest warrants, their court-ordered drug and alcohol-abuse treatment and to have their DNA samples collected. They are billed when courts need to modernize their computers.

Questions about the fairness of the criminal justice system even extend to the Supreme Court. A recent study published by Harvard Law Prof. Andrew Manuel Crespo found that in two-thirds of Supreme Court cases, criminal defense lawyers had argued fewer than two cases before the Court.

"In many instances, these lawyers were going head-to-head with lawyers from the Office of the Solicitor General, which represents the federal government at the court," writes the Christian Science Monitor's Henry Gass. "A lawyer from the Solicitor General’s office had on average made about 25 previous arguments to the court, compared with only 5.3 for the criminal defense lawyers they faced."

The study examined cases over a 10-year period that ended in June 2015.

This report contains material from the Associated Press.