Joaquin “El Chapo” Guzman is escorted to a helicopter in handcuffs by Mexican navy marines at a navy hanger in Mexico City on Feb. 22, 2014. (Eduardo Verdugo/AP)

The criminal enterprise case against Joaquin “El Chapo” Guzman, the notorious leader of the Sinaloa Cartel, rests on a whole spectrum of evidence, ranging from videotaped kidnappings and torture to detailed drug ledgers, according to prosecutors. But crucially, it also rests on cooperating witnesses — the former El Chapo associates who saw all of it go down.

President Trump has a name for those kinds of people: flippers.

To the president, they are untrustworthy underlings who turn on their bosses to help prosecutors and themselves the second they’re faced with jail time. As Trump told Fox & Friends two days after his longtime attorney Michael Cohen pleaded guilty to crimes implicating the president, the use of so-called flippers by prosecutors “almost ought to be illegal.”

Trump’s caustic criticism of a widely used practice within criminal courts both stunned and worried prosecutors everywhere — but perhaps none more so than the ones within his own Justice Department, who are about to use a whole lot of “flippers” to put El Chapo on trial for international crimes.

In a recent court filing, prosecutors on the case asked a federal judge in the Eastern District of New York to bar El Chapo’s defense team from using comments from a certain “government official” regarding “flippers” during the trial, apparently fearing it could taint jurors’ trust in prosecutors’ use of the drug kingpin’s associates as witnesses.

“A government official’s recent comments in which he criticized cooperating witnesses in a wholly separate investigation, calling them ‘flippers’ whose use probably should be illegal, have been highly publicized,” prosecutors wrote in a 100-page legal filing, detailing evidence in the case. “The government requests that the Court preclude the defense from referring to those comments during argument or questioning of witnesses. These statements have no bearing on the facts at issue in this case or the particular cooperating witnesses the government expects to call at trial.”

Trump’s negative views on cooperating witnesses came after Cohen, in pleading guilty to eight charges including tax evasion and campaign finance violations, told the court that “in coordination with and at the direction of a candidate for federal office,” he worked to keep a person from publicly disclosing information that could harm the candidate. He also said he worked “in coordination” with the candidate to make a payment to a second individual.

That candidate is believed to be Trump, and the two people they sought to keep quiet are believed to be former Playboy model Karen McDougal and adult-film star Stormy Daniels.

“I know all about flipping,” Trump told Fox’s Ainsley Earhardt on Aug. 23 in an outburst over Cohen’s turning on him. “For 30, 40 years I’ve been watching flippers. Everything’s wonderful, and then they get 10 years in jail and they flip on whoever the next highest one is, or as high as you can go. It almost ought to be outlawed. It’s not fair.”

Federal prosecutors’ request Friday to keep these comments from El Chapo’s trial would not be the first time that they have had to ask a judge to keep Trump’s rhetoric out of the courtroom.

While Trump is not named in the El Chapo brief filed Friday, federal prosecutors are almost certainly referring to him based on their citation of a trial in which Trump’s flipping comments surfaced for apparently the first time.

In a federal trial in New York on Aug. 28, an attorney for a defendant charged in a crack-cocaine distribution case tried to use Trump’s flipping comments during closing arguments. His intention: to cast doubt on the testimony of one of the prosecutors’ cooperating witnesses, who was also a drug dealer, according to an account of the trial in the New York Times.

The defense attorney, Kafahni Nkrumah, attempted to make a comparison to the trial of former Trump campaign chairman Paul Manafort, in which testimony from a “flipper” — his associate Rick Gates — was used to convict him of eight felonies, including tax and bank fraud. But prosecutors in the New York drug case immediately objected, the Times reported. Out of the jury’s earshot, Nkrumah tried to tell the judge that he wanted to explain Trump’s flipper comments to the jury because he found them relevant.

“I believe that the president’s opinion of cooperators is just as pertinent as anyone else’s,” Nkrumah told the judge, according to the Times. “He is talking about cooperators, the essence of this case.”

The judge ruled Nkrumah could not talk about it — a decision that the prosecutors in El Chapo’s case cited in support of their request to keep it out of the cartel leader’s trial.

It was the kind of episode prosecutors across the country feared would happen as a result of Trump’s comments.

Prosecutors’ use of cooperating witnesses in criminal trials is certainly not without fault, given it requires making deals with sometimes disreputable people who are looking for something to gain. But legal scholars have long acknowledged it as a flawed necessity within the criminal justice system.

Writing for Lawfare this month, Barbara McQuade, the U.S. attorney for the Eastern District of Michigan from 2010 to 2017, described the legal safeguards prosecutors use to test the credibility of cooperating witnesses, whose inside knowledge of a defendant’s crimes may be integral to proving the case. She called the president’s criticism of cooperating witnesses ignorant of this legal process, “misleading and self-serving,” as well as harmful to the law enforcement he claims to support.

“When ordinary citizens hear their president criticize the practice and say it should be illegal, jurors may become hostile to the concept of cooperation.” she wrote. The result, she said, is “it will become increasingly difficult to convict the leaders of criminal organizations.”

Neal Katyal, former acting solicitor general during the Obama administration, put it more bluntly. In an email to The Washington Post last month, in reference to Trump’s suggestion that flippers should be outlawed, Katyal wrote: “If President Trump’s views were the law, literally thousands of criminals would be on the street today.”

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