TRENTON -- After sweeping changes to New Jersey's bail system took effect this year, prosecutors and defense attorneys who joined hands in supporting the reforms are now duking it out over the ground rules.

The state Supreme Court heard arguments Wednesday in a dispute regarding evidence rules at the hearings where judges decide whether to order a defendant locked up until trial.

The changes, which virtually eliminated the cash bail system, were meant to allow judges to order violent offenders held until trial while keeping poor, low-level defendants from languishing in jail because they couldn't afford bail.

The new system has faced criticism in its first three months, but New Jersey's attorney general, its public defender and civil liberties advocates have been united in their support.

However, they found themselves back on opposite ends of the courtroom in Trenton on Wednesday, adversaries in a case with high stakes for those accused of crimes in the Garden State.

Defense attorneys argue the state is stonewalling defendants as prosecutors seek to lock them up. Prosecutors contend the defense attorneys are looking to turn early court appearances into "mini-trials."

The case that brought the issue before the court, known as State v. Habeeb Robinson, concerns a Newark murder suspect who was arrested based in part on the statements of two witnesses in early January.

Under the new bail system, a judge decides at a pre-trial detention hearing whether a defendant presents enough of a danger to be thrown in jail or should be released under a monitoring program to await trial.

If prosecutors move to have them detained, the defense is entitled to discovery, which is the legal term for the process by which the state gives someone accused of a crime access to the evidence against them.

Under the old system, defendants were only entitled to discovery later in court proceedings, often months after their arrest. But the Supreme Court dispute concerns how much discovery a defendant should get immediately after their arrest, when they have a right to due process under the constitution because the judge can now order them held without bail.

Robinson's case was one of the earliest under the new system, and his public defenders requested access to the evidence prosecutors cited in court documents seeking to have Robinson detained.

The Essex County Prosecutor's Office provided a preliminary report and an affidavit describing the evidence, but would not provide the evidence itself, which included two witness statements and surveillance footage from the scene.

The state Public Defender's Office and civil liberties advocates cried foul, arguing the ground rules for the new system require the state to provide discovery early in the process if they're looking to have a defendant locked up.

"Both court rules and the basic conceptions of fairness call for prosecutors seeking pretrial detention to produce all reports related to that decision, and the prosecution here did not produce what was legally required," Alexander Shalom, a senior attorney for the state chapter of the American Civil Liberties Union, said of the Robinson case.

Joseph Krakora, New Jersey's public defender, said judges also need access to the material to make informed decisions on the prosecutor's detention request, arguing there was "no way a judge can consider the nature and circumstances of the offense and the weight of the evidence" without broader discovery.

The judge in the Robinson case, Ronald Wigler, sided with public defenders, as did an appeals court, which issued a February decision finding the judge's ruling was consistent with the bail reform law and the court rules created to implement it. The state Attorney General's Office then brought the matter before the Supreme Court.

Elie Honig, the director of the state Division of Criminal Justice, told the justices on Wednesday that defense attorneys were wrongly painting prosecutors as acting in bad faith.

"This is not a game of keepaway," Honig said. "This is not withholding discovery for tactical purposes."

Honig said in most cases, prosecutors were refusing to release discovery to protect witnesses from intimidation and retaliation, or because prosecutors did not have enough time to review reams of paper or hours of video footage to make sure they weren't disclosing other privileged information.

Under the new bail rules, defendants make a first appearance in court within 48 hours of their arrest -- and, often, even sooner than that. That gives prosecutors little time to review their case file before handing evidence over, Honig argued.

The defense attorneys countered that defendants and the court should not have to rely on the prosecutor's summary of the evidence supporting detention instead of the evidence itself.

The court is expected to weigh in on the matter soon because the controversy affects how detention hearings across the state are handled.

S.P. Sullivan may be reached at ssullivan@njadvancemedia.com. Follow him on Twitter. Find NJ.com on Facebook.