Two years ago, a New York City man named Marcellus Johnson was convicted of robbery — in part as a result of incriminating telephone conversations that had been recorded while he was awaiting trial in a Rikers Island jail cell. Last April, New York’s highest court affirmed the conviction, upholding the use of the recorded conversations.

However, the justices of the New York Court of Appeals left open a future challenge to the use of such recordings.

“Our resolution of the narrowly drawn issues presented on this appeal,” the justices wrote, “should not be interpreted as the Court’s approval of these practices.”

These practices, the court made clear, involve the routine recording of inmate telephone conversations by corrections officials, and the nearly as routine practice of turning those recordings over to prosecutors.

Justice Eugene F. Pigott, in a concurring opinion, put the court’s concerns plainly.

“The current arrangement between the Department of Corrections and the district attorney’s office creates a serious potential for abuse,” Pigott wrote, adding, “Something needs to change.”

An effort to compel that change has now arisen in another New York case: the murder trial of Pedro Hernandez for the killing of Etan Patz, the 6-year-old boy who famously went missing in 1979, never to be found. In Hernandez’s first trial — a single holdout juror prevented a conviction last year — prosecutors used a handful of recorded jail conversations as part of their case. Now, given the Court of Appeals decision, Hernandez’s lawyers are moving to bar prosecutors from using the conversations in his re-trial, set to begin in Supreme Court in Manhattan next month.

The phone calls at issue were between Hernandez and his wife, made over the course of the four years Hernandez has been held at Rikers Island since his 2012 arrest. Prosecutors used them in an effort to undercut one of the central claims of Hernandez’s defense: that he is mentally ill and susceptible to being manipulated. Hernandez, a former worker in a bodega near where Patz lived, initially confessed to killing the boy in the bodega basement and stashing his body in a box on a nearby street. But his lawyers have said the confession was coerced and that it amounts to the invented imaginings of a profoundly sick man who has been on psychiatric medication for years. Prosecutors argued that the phone conversations revealed Hernandez to be coherent, even calculating, and thus likely faking his mental illness.

Now Hernandez’s lawyers have argued that while Hernandez may have been aware corrections officials were recording his calls to his wife, he had never consented to those recordings being given to prosecutors. They cite the April Court of Appeals decision in their filings.

“The facts at issue here,” the lawyers wrote in papers filed this summer, “shed light on the Department of Correction’s unsettling practices — practices that have turned a body responsible for detaining individuals to assure their presence in court into an evidence gathering arm of the district attorney’s office. As the Supreme Court has asserted, ‘Prison walls do not form a barrier separating prison inmates from the protections of the Constitution.’”

Prosecutors with the Manhattan District Attorney’s office have urged the judge in the Patz case, Maxwell Wiley, to reject the defense motion to bar the recorded calls.

“In brief, the defendant has consistently and frequently used the telephone while incarcerated since his arrest in May of 2012,” they wrote. “Before any inmate makes a phone call, the inmate is warned no fewer than three times that his phone calls may be recorded and monitored. The inmate is also unequivocally told that his use of the phone constitutes consent to the recording of the call. The defendant’s calls are also replete with explicit and implicit references to his knowledge that the calls are being recorded and they may be turned over to law enforcement agencies. Of course, once an inmate consents to the recording of the conversation, he no longer retains a reasonable expectation of privacy in the recordings.”

The dispute over the telephone recordings is just the latest bit of legal combat in a case that has stretched on for years and rekindled one of the darker moments in the city’s history. Etan Patz was on his way to school alone for the first time in his young life when he vanished. A manhunt followed; a national debate over parental responsibility was provoked; suspects surfaced, only to be discounted. Patz’s parents, convinced a convicted pedophile who had once dated Etan’s babysitter was the likely killer, won a civil judgment against the man, Jose Ramos.

Doubts about Hernandez’s guilt arose almost from the moment he confessed and was arrested. A former federal prosecutor who had spent years trying to convict Ramos, as well as the FBI agent who worked with him, both testified at Hernandez’s first trial about what they believed to be convincing evidence that Ramos was the actual killer. But prosecutors very nearly won a conviction, and when the jury split 11–1 for conviction and a mistrial was declared, they vowed to try again. Patz’s family, now assured Hernandez was their son’s murderer, had the earlier judgment against Ramos vacated.

It’s unclear what the chances are that Hernandez’s lawyers will prevail on the phone calls. But it seems clear that, in citing the concerns or uncertainty of the Court of Appeals, they are laying the grounds for a future appeal should Hernandez be convicted.

Justice Pigott, to be sure, laid out his concerns at length in his April opinion.

He and the other justices made clear they understood the need for corrections officials, in the interest of safety, to be able to record calls of the often violent people in their custody. And there seems no evidence that calls between inmates and their lawyers are being recorded and improperly used against defendants. It’s the wholesale recording of calls and the pro forma providing of them to prosecutors that seemed to trouble Pigott, a Republican who is considered to be a conservative jurist.

“The department’s purpose in recording and monitoring these conversations is limited to ensuring the safety and security of its facilities, not harvesting evidence for the prosecution,” he wrote. “Yet the people admit that, unknown to defendants, they routinely obtain and review such recordings before trial, in search of anything that can be used against them. The People justify this practice principally on the basis of consent: because the calls were recorded by the Department, and the detainee knew the department could record and or monitor the calls, he has no expectation of privacy in the conversations and is not entitled to shield them from the prosecution.”

Pigott then cites the language of a prior ruling, saying there is “a major distinction between prison authorities having access to prisoners’ phone calls for purposes of prison security and discipline, and the prosecutors of that pretrial prisoner having the same access for purposes of gaining advance knowledge of the pretrial prisoner’s trial strategy and potential witnesses.”

Prosecutors in the Patz trial suggest that is hardly the case with Hernandez’s calls. They didn’t involve witnesses or strategy. As well, they argue, his wife reminds Hernandez during one or more of the calls that he shouldn’t say anything that could be damaging. They argue there is evidence Hernandez had been told by his own lawyers to watch what he said on the calls, for fear it could be used against him. In essence, that’s consent, they argue.

Whether the Hernandez case is the one that ultimately tests the nature and extent of the concerns of the Court of Appeals, it seems inevitable some case will, given the apparent invitation.