Few homicides have gripped the District, even the nation, as much as the killing of Chandra Levy, a 24-year-old Washington intern with the Federal Bureau of Prisons who was having an affair with a married congressman when she disappeared in 2001.

Levy’s skeletal remains were found in Rock Creek Park about a year later, but it wasn’t until 2009 that authorities charged the man they said had killed her: an undocumented immigrant from El Salvador and onetime gang member who had previously been convicted of assaulting two women in the Northwest Washington park.

When a jury found Ingmar Guandique guilty of murder in 2010, it seemed as if the case had finally come to a close. But two years later, that conviction was overturned and a new trial ordered after questions surfaced about a key witness in the case. Then, just months before the second trial was to begin, prosecutors in 2016 abruptly dropped all charges against Guandique. So far, no one has been held to account for Levy’s killing.

Now, two of the lead attorneys who prosecuted Guandique are facing allegations that they mishandled the case by failing to appropriately reveal information that cast doubt on the credibility of their star witness.

Beginning on Tuesday, former ­assistant U.S. attorneys Amanda Haines and Fernando Campoamor-Sanchez are set to face a D.C. lawyer ethics panel during a rare, week-long public hearing.

Officials with the D.C. Office of Disciplinary Counsel allege that Haines and Campoamor-Sanchez did not disclose that their witness Armando Morales, a five-time felon and former gang member, had previously provided information to law enforcement officials in a separate criminal case. Morales testified at Guandique’s trial that he had never before cooperated with authorities.

Prosecutors are required to provide the defense all pertinent evidence before trial to allow defense attorneys time to investigate the findings. Prosecutors must disclose the information even if the evidence jeopardizes their case. Failure to do so could result in a case being retried or thrown out by a court and the prosecutor being disciplined.

Attorneys for Haines and ­Campoamor-Sanchez call the ethics allegations unfounded and say information regarding Morales’s dealings with prosecutors had been shared — a contention the defense attorneys and the Disciplinary Counsel dispute.

“Mr. Campoamor-Sanchez denies the charges against him. He respects the Board’s process and looks forward to demonstrating that he acted appropriately,” attorney Mark Lynch said in an email.

Justin Dillon, an attorney for Haines, said the Justice Department’s Office of Professional Responsibility investigated the allegations for two years and then “cleared” her of misconduct. A Justice spokesman declined to comment on the investigation.

Dillon, also a former federal prosecutor, said Haines retired this month after 30 years as a litigator, more than 20 years of which was spent as a prosecutor in Washington. The 59-year-old Haines, Dillon said, remains licensed to practice law in ­Washington and New York. Dillon questioned why the Disciplinary Counsel was “still going after her, especially now that she’s retired.”

Hamilton P. Fox III, the lead attorney for the Disciplinary Counsel, said that as long as Haines maintained her law license, her retirement would not exempt her from being investigated for potentially violating law practices. Fox added that lawyers are not allowed to resign from the bar while a disciplinary matter is pending.

The ethics allegations are based on the prosecutors’ most critical link between Guandique and Levy. In 2006, Morales shared a cell with Guandique in a federal prison in Kentucky. Guandique was serving time for assaults on women in Rock Creek Park that occurred around the time Levy disappeared.

Morales told prosecutors Guandique told him that he accidentally killed Levy while trying to rob her. At trial, Morales testified about Guandique’s alleged confession. Guandique’s public defenders asked Morales if he had ever cooperated with authorities in exchange for favors. Morales said that the Levy case was his first time providing such cooperation and that he received no benefit from authorities.

Morales’s testimony was key for the prosecution because there was no forensic evidence or witness linking Guandique to Levy’s death.

Attorneys for the two former prosecutors contend that their clients notified Guandique’s attorneys that Morales had been “debriefed” by authorities in 2008 or 2009 about his own gang activities. That information, the prosecutors said, was contained in a three-page letter they provided to Guandique’s attorneys before Morales took the stand. The first page of the letter outlined that meeting between Morales and law enforcement.

But Guandique’s attorneys said the letter they received was missing the first page. The prosecutors’ attorneys argue that if the public defenders did not received the first page, they should have requested it because Pages 2 and 3 were clearly identified by numbers at the top of each page.

Prosecutors also contend that debriefing and cooperation are not the same. Debriefing, they say, is questioning a defendant about details of a case. Cooperation, they say, is asking a defendant questions and then, in exchange for the answers, offering the defendant some type of incentive such as a reduced sentence or relaxed prison conditions.

Guandique maintained that he knew nothing about Levy’s death and told a Washington Post reporter in a letter that he was merely a “scapegoat.” Still, the D.C. Superior Court jury convicted him on two counts of first-degree felony murder, related to Levy’s kidnapping and attempted robbery. He was sentenced to 60 years in prison.

In 2012, two years after Guandique’s conviction, Haines and Campoamor-Sanchez learned of another meeting between Morales and law enforcement. In 1998, Morales had given authorities information about two murders, provided names of the alleged murderers, discussed his own involvement in one of the killings and offered to testify, according to a filing by the Disciplinary Counsel.

The prosecutors disclosed the newly obtained information to Guandique’s public defenders, who then asked a judge to order a new trial. The defense said that the prosecution’s star witness had lied to the jury about previous dealings with law enforcement and that such information might have caused jurors to question Morales’s credibility.

Supervisors within the U.S. attorney’s office then decided that, given the post-trial discovery of Morales’s 1998 cooperation with authorities, they would agree to a second trial. That trial was set for 2016, and a new team of prosecutors was to handle the case.

As those prosecutors were ­preparing for trial, they discovered new information about Morales. Washington Post articles detailed how Morales had allegedly boasted to a Maryland woman that he lied when he testified at trial about Guandique’s confession. Morales met the woman in early 2016 after his release from prison.

The woman began secretly recording her conversations with Morales and then played the recordings for attorneys and prosecutors in the Guandique case.

With Morales’s credibility under greater scrutiny, the government dropped all charges against Guandique. He was released from prison and deported in 2017.

Before leaving their longtime careers as prosecutors, Haines and Campoamor-Sanchez spent decades fighting for convictions on behalf of victims of violent crimes and their families.

Haines specialized in cold-case homicides and gained a reputation of closing difficult cases and securing convictions, often with hard-nosed, dramatic presentations before juries.

After the Guandique trial, Haines left the U.S. attorney’s office in Washington and worked as a prosecutor on capital murder cases for the Justice Department. After resigning from the department, she relocated to Massachusetts and was an attorney for the Department of Homeland Security until her retirement.

Before the Guandique trial, Campoamor-Sanchez, 52, had spent years prosecuting federal crimes within the U.S. attorney office’s National Security section focusing on kidnappings and killings of American citizens overseas.

After the trial, Campoamor-Sanchez sought a nomination for a D.C. judgeship. But when Guandique’s attorneys requested a new trial, he withdrew his name. He now works as a trial attorney with the Securities and Exchange Commission.

Haines and Campoamor-Sanchez are coming before a board that reviews complaints on behalf of the D.C. Court of Appeals. Attorneys said a decision could take about a year.

If found guilty of any violations, the former prosecutors could face a range of punishments from public reprimand, to suspension, to having their bar licenses revoked as part of disbarment.