As U.S. prosecutors rest their case against Mexico's former top cop during a trial in New York City, another question is in play: Are U.S. efforts to stem the flow of deadly Fentanyl from Mexico into the United States doing any good?
Four years ago, the conviction of Joaquín "El Chapo" Guzman Loera gave prosecutors many other threads to pull on the web of crime and corruption that enables the transnational drug trade.
Cooperating witnesses in that trial named two top Mexican law-enforcement figures as accomplices. One was the man now on trial – Genaro Garcia Luna.
Garcia Luna served as both the head of Mexico's FBI and then in the president's cabinet as secretary of Public Security. During his tenure, he met with U.S. officials and spoke at Washington think-tanks about fighting the "war on drugs."
At the time, NPR reported on suspicions that the Mexican government was favoring the Sinaloa drug cartel as it fought a vicious war for supremacy against other traffickers.
Luna was arrested in Dallas, Texas, in 2019 and stands accused of accepting millions of dollars at secret meetings with cartel bosses.
Former drug-traffickers in U.S. custody have testified in colorful detail about the lawman on the take, about handing over $3m in cash a meeting at a Guadalajara car-wash, and Garcia Luna's alleged role in helping Guzman narrowly escape arrest.
On Monday, the star witness was Jesús "El Rey - The King" Zambada García. Zambada Garcia told jurors about packing duffle bags holding millions in cash which he watched Garcia Luna collect from one of the Sinaloa cartel's lawyers.
Zamabada described how paying about $1.5 million dollars per month to government officials allowed his men to integrate completely into Mexican law enforcement agencies - even wearing government uniforms as they raided rival cartels or made sure to escape raids themselves.
"The government supported us," Zambada said.
But defense lawyers have pointed out at every turn that the prosecution's case is all hearsay – most of it from convicted narcotraffickers who have won great reductions in their prison sentences in exchange for their cooperation.
A drug trial playing out against the rise of Mexican cartels
This trial is unfolding during at a time when the two major Mexican cartels, the Sinaloa Cartel and Jalisco New Generation (CJNG) have only grown in power and wealth.
In recent years, rival drug traffickers launched waves of gang violence inside Mexico. They also fueled an explosion of drug deaths in the U.S. by trafficking illicit fentanyl.
More than 108,000 people in the U.S. died from drug overdoses 2021 alone, a spike driven largely by fentanyl.
"We're losing the battle," says Rep. David Trone (D-Maryland) in an interview with NPR. "Mexico, they're not helping us."
Efforts to target the cartels inside Mexico unraveled four years ago when the U.S. attempted to prosecute another top Mexican official, retired Defense Minister Salvador Cienfuegos Zepeda.
Cienfuegos was arrested in Los Angeles in 2019, during the final months of Donald Trump's presidency. But in a highly unusual move, charges against Cienfuegos were dropped and he was returned to Mexico.
Facing intense pressure from the government of President Manuel Lopez Obrador, the U.S. DOJ filed court documents unsealed in November 2020 stating that "foreign policy considerations outweigh the government's interest in pursuing the prosecution of the defendant."
Following that diplomatic crisis, cooperation between U.S. and Mexican law enforcement never fully recovered, despite years of delicate negotiations.
"It's a long slog. You don't see results in a year or three years," says Regina LaBelle, who served as acting director in the White House Office of National Drug Control Policy during the first year of the Biden administration.
In an interview with NPR, LaBelle says she believes international law enforcement and diplomatic efforts will eventually erode the cartels' power.
"We're not going to just throw up our hands and say it's impossible," she says. "Just asking Mexico to enforce more, to do more seizures in country obviously isn't going to do it."
Indeed, many U.S. officials and law enforcement now believe key Mexican leaders and police officials have been corrupted by the cartels money or intimidated by their growing military power.
As a consequence, drug policy experts say the cartels are free to operate fentanyl and methamphetamine drug labs inside Mexico with near-total impunity.
A trial in New York, a wave of death and a fight in Washington DC
It's unclear what can be done about the increasingly deadly drug trade.
Republicans have made the Mexican cartels, the fentanyl crisis and border security into a major line of attack, arguing the Biden administration can do far more to stop traffickers.
"Last year, drug overdose deaths hit a record high – fueled by fentanyl," wrote House Speaker Kevin McCarthy last week on Twitter. "Securing our southern border would help address this crisis and save lives."
Last year, drug overdose deaths hit a record high – fueled by fentanyl. Securing our southern border would help address this crisis and save lives.— Kevin McCarthy (@SpeakerMcCarthy) February 8, 2023
Biden acknowledged the scale of the fentanyl crisis during his state of the union address, calling for "a major surge to stop fentanyl production and sale and trafficking."
Republicans responded with jeers and catcalls, but they have yet to offer a plan of their own for targeting fentanyl smugglers that experts say might significantly reduce the supply reaching American streets.
In part that's because stopping the flow of fentanyl is uniquely difficult.
The synthetic opioid can be made far more cheaply than other drugs. It's so powerful, it can be smuggled profitably even in tiny quantities that are nearly impossible to detect.
"My belief is there's absolutely no way to stop it," says Rep. Trone, who voiced skepticism about the willingness of Mexican officials to target cartels.
"It's not our country, it's their country. They've chosen not to go after the drug traffickers," he says.
Many drug policy experts are also skeptical that prosecutions like that of Genaro Garcia Luna will have much impact.
If he is eventually found guilty, his trial in New York City might offer a portion of justice to U.S. families devastated by the fentanyl crisis.
But there's no sign cases like this one have weakened the Mexican cartels or helped the Mexican government reduce corruption.
After decades of the drug war, the cartels appear to be stronger and wealthier than ever, largely because of the booming fentanyl trade.