Last year, Philadelphia police narcotics officers sent confidential informants to buy drugs from a house in North Philadelphia and then — based on the informants’ report — issued an arrest warrant for a man named Encarnacion Guzman on drug-dealing charges.

Now, Philadelphia’s public defender is arguing not only that the case against Guzman is built on false information, but that it’s part of a pattern that calls into question any testimony by officers of the department’s Narcotics Bureau.

In a motion requesting all documents and evidence related to Guzman’s case, the defender referenced an incident that has hung over the bureau since 2017, when a commanding officer allegedly encouraged a practice of falsifying reports to flip those facing arrest into off-the-books informants.

The filing also documents numerous incidents of misconduct within the Narcotics Bureau — which includes more than 150 officers across a strike force, a field unit, and an intensive drug investigation unit. The incidents, many of which have not previously been reported, include nine cases thrown out after video evidence discredited police accounts; a pattern of prosecutors withdrawing cases involving one unnamed, “problematic” informant; a squad of officers who were found in multiple cases to have fabricated paperwork or used threats of false arrest to flip informants; and two officers arrested for perjury within the last year.

The Defender Association acknowledged the motion filed this month is only partly about Guzman’s case. It hopes to use it to force a broader reexamination of a dormant probe into whether narcotics officers have been systematically falsifying reports. Because the District Attorney’s Office “dropped the ball with their responsibility to look into this,” Defender Association lawyer Michael Mellon said, he wants the courts to intervene.

“It’s our position there are hundreds of cases they will need to reverse,” he said.

And, he argued, cases going forward also demand careful review. “The recent history of misconduct by numerous members of the Narcotics Unit, including its supervisors, supports the argument that any determinations by the court must be made by examining the record of the unit as a whole and not in a vacuum,” he said.

A police spokesperson declined to comment on the motion because it referenced ongoing investigations. A spokesperson for the district attorney said the office “is applying due diligence to this motion and exploring all available options for an appropriate response, which could include issuing subpoenas to ensure discovery obligations are met.”

Though the motion is unusual, it aligns with a broader push to track when police are caught in lies — including a New York City pilot program launched by the state court system this year to monitor such incidents — and to act on such misconduct, said Julia Simon-Kerr, a University of Connecticut law professor who studies evidence and credibility.

“It is the other side of the coin of this issue of police brutality,” she said. “In the same way that we haven’t had good methods of keeping track of police brutality by particular officers, there has been even less keeping track of lying by officers.

“Unless we know what’s going on,” she added, “it’s very hard to know whether this is a systemic problem and we should be discounting or discrediting testimony or not.”

It also aligns with another common but controversial concept in criminal cases, the right of prosecutors to tell jurors about a defendant’s prior “bad acts” if an alleged crime seems to fit a pattern of misconduct.

Legal experts differ on whether a motion such as the Philadelphia defenders’ is likely to carry weight.

Pace University law professor Bennett Gershman said a theory that sounds like “guilt by association” wouldn’t hold up. “A judge would say, ‘No, it’s not relevant,‘” he said, unless the officer involved in the arrest had been shown to have a history of perjury.

The defenders did not document any instances of perjury by the officers who made the case against Guzman, who turned himself in after learning that an arrest warrant had been issued based on drug sales reported by confidential informants. However, during an Internal Affairs investigation, one of those officers acknowledged being aware of instructions to falsify paperwork for potential informants, and in at least one case followed orders to interview and release such an informant without charges.

Instead, the filing cites cases like a raid on a Southwest Philadelphia deli in March 2019, when Narcotics Strike Force Officers Duane Watson and Richard Rivera arrested five people for drug transactions, allegations contradicted by surveillance video.

One case was withdrawn after a judge viewed the video and found Watson’s testimony not credible, according to the filing. Watson was arrested for perjury on Feb. 25, 2020. (He and a lawyer representing him did not respond to requests for comment.)

A second case was dropped in July 2019 after Watson’s partner, Rivera — who the defenders say had testified falsely at a preliminary hearing in the same case — refused to testify. Rivera retired from the Police Department in December.

In an interview, Rivera said he did not recall the deli case, noting he worked more than 20,000 cases, and did not know the details of the charges against his former partner. He said there are many legitimate reasons why he might have refused to testify at the trial.

“The last three years haven’t been good for Narcotics,” he said, acknowledging recent arrests in the department, including Officer James Coolen, for using a confiscated Porsche; Officer Charles Myers, for perjury; and Officer Stanley Davis, for trading drugs for sex in his police car.

Rivera said he and his squad were diligent in their work: “I’ve never seen anything out of the ordinary. If it was wrong or illegal, I know my squad would speak up. Everyone there got over 20 years in, and they’re not going to ruin their career for something stupid.”

Paula Sen, the public defender who handled that case, said video showed that the officers had stopped and frisked everyone at the deli during the raid without cause. She questioned Rivera’s lack of recall: “Either lying in police paperwork and authorizing or looking the other way in unconstitutional searches and seizures and arrests is so part of his daily activity that it doesn’t stand out in any way — or he’s lying.”

Incidents where video or other evidence discredited officers’ statements spanned both the Narcotics field unit and its strike force.

Two separate judges found a pair of strike force officers could not have smelled marijuana in stops of moving vehicles. Another officer was deemed to be not a credible witness after his testimony contradicted his own paperwork. And one narcotics field unit squad was found to have falsified arrest paperwork in order to “flip” informal informants; threatened in a voice mail to arrest a defendant’s girlfriend if he would not flip; and omitted potentially exonerating information from multiple arrest reports. All of those cases were thrown out.

Jules Epstein, a Temple University law professor, said that if the Defender Association prevails in persuading a judge to consider this collective history, it could change how narcotics cases are prosecuted in Philadelphia.

“In a particular case, they may have other strong corroborating evidence — fingerprints or body cam” supporting an officer’s testimony, he said. “But what it does is, it gives the jury more facts to weigh. And this type of proof would remind juries that police don’t get an edge on credibility and, yes, sometimes police lie, too, just like some civilians do.”