CHICAGO — Back when a Brownsville, Texas, teenager pleaded guilty in 2006 to assaulting an officer in the police station, he didn’t know the station’s cameras had captured the scuffle on video.

When the video emerged approximately four years later in an unrelated case, it appeared to show that the officer, not the teen, had instigated the altercation.

The Texas courts soon after declared George Alvarez innocent. Alvarez, who initially had been arrested on charges of public intoxication and suspicion of car burglary, then filed suit and won a $2 million verdict from a U.S. District Court jury.

But that verdict was thrown out in August by the Fifth Circuit U.S. Court of Appeals, which ruled that prosecutors are not required under the constitution to turn over evidence of defendants’ innocence before they plead guilty.

Now Alvarez’s lawyer is asking the U.S. Supreme Court to take up an appeal of that decision, contending “the justice system’s integrity and the liberty of innocent defendants are threatened” when exculpatory evidence is withheld. The court is to consider next month whether to take the case after Brownsville attorneys respond.

The issue arises amidst growing recognition that in a system built on plea bargains – more than nine of every 10 criminal convictions across the country are based on guilty pleas – there is the risk that innocent suspects nevertheless plead guilty.

A nationwide team of reporters has been exploring the phenomenon, which at first blush is contrary to logic. The team has identified more than 130 cases nationwide in which defendants entered guilty pleas despite significant evidence of their innocence.

Such instances occur for a variety of reasons, but commonly involve defendants who don’t want to risk trial out of fear they will lose and receive a far harsher sentence than if they plead guilty.

“Without access to exculpatory evidence, innocent defendants face substantial, sometimes overwhelming, pressure to plead guilty,” Alvarez’s petition to the U.S. Supreme Court states.

The U.S. Supreme Court first ruled in 1963 in Brady v. Maryland that the prosecution musts turn over, upon request evidence that is favorable to the defense either in establishing guilt or in the penalty phase, and that whether the prosecutor acted intentionally did not matter. That duty, later cases make clear, extends to the entire prosecution team, including police.

Left unanswered was how quickly in the process that evidence had to be turned over.

In a later case, U.S. v Ruiz, the Supreme Court ruled prosecutors had no duty to turn over impeachment evidence — evidence that cast doubt on their witnesses — before a guilty plea. Since then, courts have expressed conflicting views on whether that ruling also extends to evidence of a defendant’s innocence.

In addition to the Fifth Circuit, which oversees courts in Texas, Louisiana, and Mississippi, courts in the Second Circuit and Fourth Circuit have cited Ruiz as they expressed doubt that prosecutors have to turn over such exculpatory evidence before a guilty plea.

The Seventh and 10th Circuits, in contrast, have held that such a duty likely exists. The Seventh Circuit wrote in a 2005 case that the U.S. Supreme Court was “highly likely” to find it unconstitutional for prosecutors to withhold strong evidence of a defendants’ innocence before they pleaded guilty.

That was the issue facing West Virginia Supreme Court of Appeals in the 2015 case of Joseph Buffey.

Buffey, then 19, had been arrested in 2001 in connection with a string of burglaries of business that occurred around the time of the home invasion of an 83-year old woman who was the mother of a Clarskburg police officer. Buffey initially denied any connection to the home invasion.

But within weeks, based on the warnings of his lawyer that he could face a much harsher sentence if he went to trial, Buffey told the judge that he “broke into an elderly lady’s house and robbed her and forced her to have sex with me,”

He was given a sentence of between 70 and 110 years.

At the time he entered that plea, neither Buffey nor his attorney knew that police had DNA evidence that cast doubt on his guilt.

The Innocence Project later took on Buffey’s representation, and won new DNA testing in 2010 -- testing that excluded Buffey as the primary or secondary source of DNA. Further, the testing connected the sexual assault to the victim’s paper boy, who had a history of sexual violence.

In overturning the conviction, the West Virginia Supreme Court ruled that the prosecution had violated Buffey’s due process rights by withholding the results of the original DNA tests before he pleaded guilty.

Even then, the prosecutors declined to drop the home invasion charges. He was offered a new plea offer that he accepted: Plead guilty to burglary and be immediately released. He entered a so-called Alford plea, insisting he was innocent while acknowledging there was sufficient evidence to be convicted at trial.

Nina Morrison, the Innocence Project attorney who helped win Buffey’s release, said in an interview that she believed “most prosecutors if they become aware of it will promptly turn over evidence of someone’s innocence.”

Even so, organizations of defense lawyers and professors cited additional instances in which innocent people have pled guilty and spent years in custody because they were not told that prosecutors were holding evidence of their innocence.

One was Stephen Brodie. After Richardson, Texas, police picked him up for robbing money from a soda machine in 1991, they thought he might have been the man who had broken into a home and sexually assaulted a five-year old girl. Brodie is deaf, and the girl had described her attacker as having a strange voice.

Brodie was questioned for days before he provided a confession during which he got several details wrong, according to the court record. He also confessed during that interrogation to several crimes that the police had made up.

Nevertheless, Brodie was sentenced to five years in prison, and remained locked up when his sentence was complete because he refused to sign a sex register.

What his attorneys did not know: The prosecution team had withheld evidence of his innocence. Hair found on the victim’s blanket did not match Brodie, the victim, or anyone in the victim’s family, A fingerprint found on the window screen matched that of a convicted child rapist who was suspected in a number of other assaults in the area.

That evidence only surfaced years later, after a new district attorney took office and established a conviction integrity unit. Spurred by a letter from Brodie’s father, a paralegal in that office began examining the case and discovered the exculpatory evidence.

Brodie won a declaration of “actual innocence” from the Texas Court of Criminal Appeals in 2010.

Dale Duke of Dallas, Texas, spent 14 years in prison after he pleaded no-contest to aggravated assault, based on allegations by his step-daughter that he sexually abused her after he and his wife broke up. The girl later recanted, but Duke remained imprisoned.

He was freed only after evidence emerged that prosecutors knew before Duke pleaded guilty that the girl’s maternal grandmother had cast doubt on the accusation.

Defense attorneys warn that withheld evidence may never be uncovered in guilty plea cases, and at times is discovered only by happenstance.

Alvarez, the defendant whose case is now before the U.S. Supreme Court, was 17-years old, a ninth-grade student in the special education program, when he was brought into the Brownsville police station. The pay phone he was provided failed to work, and Alvarez began banging on it and made an obscene gesture.

As officers directed him to a padded cell, according to the record, the scuffle erupted that led to charges he had assaulted Officer Jesus Arias. Alvarez pleaded guilty in March 2006, and was given an eight-year suspended sentence with the condition he undertake treatment for substance abuse. When Alvarez failed to complete the treatment program, he was imprisoned to serve the eight years.

About four years later, lawyers for Jose Lopez, another defendant who contended he was beaten by jailers and falsely charged with assault, learned of undisclosed recordings of incidents, including that of Alvarez, in the hands of police.

Alvarez then filed a state court petition for habeas corpus, contending the video had been improperly withheld. That petition led to the state appellate court overturning the verdict and issuing the declaration of innocence.

Alvarez subsequently sued the city in federal court, leading to a $2-million jury verdict, plus attorney fees, that the city then appealed to the Fifth Circuit U.S. Court of Appeals.

Thirteen of the 16 judges then on the Fifth Circuit court agreed last August that Alvarez’s successful verdict must be overturned. The majority ruled that the law “does not affirmatively establish that a constitutional violation occurs when Brady material is not shared during the plea bargaining process,” setting a limit on the prosecutors’ duty first established by the U.S. Supreme Court in Brady v. Maryland.

“If there’s new evidence of innocence, shouldn’t a person be able to raise that even if they took a plea ... and swore that they were actually guilty, shouldn’t they be allowed to test that evidence?,” asks Adele Bernhard of the post conviction innocence project at New York Law School. “That’s where the courts are struggling.”