By Joaquin Sapien, ProPublica

The year was 1990. George H.W. Bush was president. The song "Hold On" by Wilson Phillips was number one on the Billboard chart. And Charles "Joe" Hynes, celebrated for his role as a special prosecutor in a racially charged case in Howard Beach, began his first term as Brooklyn District Attorney.

Bush's presidency came and went; his son's did too. Wilson Phillips went on a 10-year hiatus; then got back together in 2004.

Hynes, all along the way, has done exactly what that top 1990 ballad instructed: He's held on. He's been Brooklyn's top law man for nearly 24 years, making him one of the longest serving district attorneys in New York City history.

But Hynes's once firm grasp on the position could be imperiled. Buffeted by controversial cases, charges of misconduct in his office, and concerns about possibly preferential treatment for Jewish residents of the borough, Hynes is seen by political strategists to be facing a serious challenge from Kenneth Thompson, an African-American former federal prosecutor. On Tuesday, Sept. 10, voters in the Brooklyn Democratic primary could deny Hynes a chance at a seventh term.

Almost all prosecutors who stay in office for lengthy terms wind up facing a familiar array of complaints – about cases lost, creeping arrogance, political gamesmanship. Robert M. Morgenthau, revered by many across his decades as Manhattan's top prosecutor, had his share of critics and embarrassments, the troubled prosecution of five teenagers for the rape of a woman in Central Park among them.

Some of the complaints about Hynes, then, fit that mold: He's been accused of hiring and firing people based on favoritism and political connections and he's been taken to task for some failed or underwhelming prosecutions. Even his once reliable base of support, the borough's Orthodox Jewish community, has seemed to split, some angered that Hynes has made a series of pedophilia cases against people in their ranks, others disappointed that he was late to the issue and overly lenient in his handling of the cases.

But Thompson, who served in the U.S. Attorney's Office for the Eastern District of New York, has focused his criticism on the question of wrongful convictions and possible misconduct by prosecutors over the years in Hynes's office.

On the campaign trail Thompson, for instance, has cited withering criticism from two federal judges over the way one of Hynes's top prosecutors won a wrongful conviction in a high-profile murder case.

In the last several weeks, Thompson has gained endorsements from the Service Employees International Union, the Citizens Union, and several Brooklyn-based representatives in Congress.

Hynes has defended the work of his office, rejecting any claims that he permits or encourages misconduct. He has campaigned on what he asserts are his myriad novel and effective approaches to fighting crime.

Both the district attorney's office and Hynes's campaign did not respond to requests for comment.

Little public polling has been done in the race. Turnout could play a role. And Hynes, whatever his arguable travails, has history on his side.

No incumbent district attorney has lost an election in any of New York's boroughs since 1955. A Brooklyn district attorney hasn't been unseated via the vote since 1911.

Here are some issues that may figure into the election's outcome.

Michael Vecchione

Some of Hynes's campaign woes can be traced to the conduct of Michael Vecchione, the head of Hynes's Rackets Bureau. He's a polarizing figure who has drawn heavy criticism for his conduct in and out of the courtroom.

Two federal judges have lambasted Vecchione for withholding evidence and for his handling of several witnesses in a high-profile murder case.

Now the defendant, a Brooklyn man named Jabbar Collins who spent 16 years in prison, is suing the city for millions as part of a far-reaching wrongful conviction lawsuit. His lawyer, Manhattan-based attorney Joel Rudin, is attempting to make the case that misconduct in Hynes's office is so pervasive that Hynes must have actually condoned it.

Vecchione's career in the district attorney's office spans more than two decades. In 2003, the district attorney's office was forced to vacate the conviction of a man they suspected of being involved in at least three murders when a federal court agreed to hear allegations that Vecchione had withheld evidence in the man's trial.

In 2006, Vecchione tried to prosecute former FBI agent R. Lindley DeVecchio for helping arrange the murders of gangsters on behalf of mob boss Greg Scarpa. Hynes called it "the most stunning example of official corruption [he] had ever seen." But the case fell apart just days into trial when it became clear that Vecchione's chief witness was unstable and had given false testimony.

More recently, The New York Post reported that Vecchione instructed staff not to preserve exculpatory evidence in sex-trafficking cases during a training session in 2012.

Vecchione has denied all charges of misconduct, and he testified under oath that he did not remember the details of what took place at the training session for sex-trafficking cases in 2012.

Hynes has staunchly defended Vecchione, who continues to be one of the highest-paid prosecutors in the office. Earlier this year, Hynes allowed Vecchione to be a featured character in a CBS television show called Brooklyn DA.

ProPublica in 2013 has published a series of articles investigating prosecutorial misconduct and the lack of consequences for prosecutors who commit serious violations of the law. Vecchione was the subject of one of those articles.

Hynes's office did not respond to ProPublica's request for comment on Vecchione's history and its possible impact on Hynes's re-election effort.

50 Possibly Troubled Cases

Last spring, Hynes asked a judge to vacate the conviction of a man his office had mistakenly prosecuted for the murder of a Brooklyn rabbi. Hynes blamed a detective in the case for the wrongful conviction, and ordered his office to review 50 cases involving the detective.

The investigation has obvious implications for the now-retired detective, Louis Scarcella, who has publicly denied he ever did anything wrong. But Hynes's prosecutors had vouched for the detective's work in the cases, using the confessions he had allegedly won or the evidence he had produced to send people to prisons. Two of the prosecutors involved in Scarcella cases have gone on to work as New York State judges; four are now senior officials in the district attorney's office.

Thompson and other critics of Hynes pounced when it became clear that a 12-member panel of lawyers and judges appointed by Hynes to oversee the review of the 50 cases included three people who had donated to Hynes's campaign.

Hynes has said he is convinced of the panel's independence, and that the investigation will go where the evidence takes it.

The New York Times reported Friday that its examination of some of Scarcella's cases showed that prosecutors either ignored warning signs or made missteps of their own.

Hynes told the Times that the investigation so far had not turned up evidence that would require revisiting the propriety of a conviction. But he did not address the paper's findings about the conduct of his prosecutors.

Detaining Witnesses

Hynes's training procedures and office policies have also come under fire.

A Brooklyn man seeking to have his murder conviction overturned has accused Hynes's office of holding a witness against his will until he agreed to testify as prosecutors wanted in the case.

That case, which is now before a federal judge, has fueled an effort by Jabbar Collins's lawyer to establish that Hynes's office routinely detained and coerced witnesses in violation of the law. The accusation, made as part of Collins's lawsuit against Hynes and the city, deals with a powerful legal tool called the material witness order. The orders are supposed to be used only under rare circumstances, usually when prosecutors fear a potential witness might flee instead of testifying in court.

New York law requires that prosecutors bring any material witness straight to court.

But Collins's lawyer, along with several other defense lawyers are seeking to hold prosecutors accountable for abusing the orders, alleging that witnesses were never brought before a judge or provided with a lawyer, as the law requires.

Hynes has denied allegations that his prosecutors failed to abide by the law in their handling of witnesses.

Favoritism

Hynes's hiring and firing decisions have also proven fodder during the campaign, and Thompson has seized on them.

The New York Post reported this summer that Mark Posner, a lawyer in the office's powerful Rackets Bureau, was caught using his office phone to call prostitutes. The Post article said Posner was found out by his own colleagues, who were investigating a local prostitution ring.

Posner is the son of a longtime ally of Hynes, Charles Posner. The elder Posner had served as Hynes's liaison to Brooklyn's Orthodox Jewish community, and Hynes had later recommended him for a judgeship. Posner, who died in 2004, served as a State Supreme Court justice for nearly a decade.

Hynes did not fire Mark Posner after learning of his misconduct. Instead, he suspended him for 10 days and transferred him to the Early Case Assessment Bureau, a low-level desk where prosecutors analyze arrests and make judgments on what charges to pursue.

At the time Posner was caught, Brooklyn DA spokesman Jerry Schmetterer told the Post that Hynes acted as soon as he learned of Posner's conduct by suspending him, ordering him to seek counseling, and demoting him.

Posner didn't immediately respond to a voice message left at his home. And neither Hynes's office nor his campaign responded to questions from ProPublica.

In January 2012, Hynes hired a woman named Angel DiPietro to become an assistant district attorney. It was a hire with a backstory.

Eight years earlier, DiPietro was a witness in the murder case of Mark Fisher, a Fairfield University student-athlete in Prospect Park South. She was with Fisher and friends in Brooklyn the night he was killed. At the time, a spokesman for the police department told the New York Times that DiPietro demonstrated "a lack of full-hearted cooperation." Police Commissioner Ray Kelly himself described DiPietro and seven of her other friends as "uncooperative."

Eventually DiPietro testified at trial and two people she was with that night were found guilty of the murder.

DiPietro's father, a defense attorney in Brooklyn, had been a regular contributor to Hynes's political campaigns, and in the months after DiPietro was hired, he donated another $3,000 to Hynes's 2013 political campaign.

DiPietro, contacted by telephone, referred ProPublica to the spokesman for the district attorney's office. The spokesman did not respond to request for comment.

James DiPietro, Angel's father, did agree to an interview.

"I wish I could've given him more," DiPietro's father said of his donations to Hynes. He said that his daughter was first offered the job in 2010 and fully deserved it on her own merits. And he asserted that his daughter had in fact cooperated fully in the Fisher murder investigation.

Selective Prosecutions

In 1996 Hynes indicted a Brooklyn political gadfly named John O'Hara. The charge was modest: voting from his girlfriend's apartment, which was outside of his own election district. After three separate trials, O'Hara was found guilty, lost his law license, and was sentenced to community service.

O'Hara has always claimed that Hynes went after him because he'd run for city council and assembly seats against some of Hynes's allies.

Thirteen years later, in 2009, a grievance committee bolstered O'Hara's account. It restored his license, saying there were "grave doubts that Mr. O'Hara did anything that justified his criminal prosecution."

In 2012, The New York Times ran a stinging series of articles on how Hynes's office for years handled investigations of accused sexual predators in the Orthodox Jewish communities. The series established that Hynes had allowed many of the accusations to be handled by rabbinical courts rather than prosecuting the cases himself.

Hynes initially defended the way he handled the sex abuse cases, but eventually pledged reforms and began prosecuting them with more vigor.