Jeff Leen is The Washington Post’s assistant managing editor for investigations.

An extraordinary claim requires extraordinary proof. That old dictum ought to hang on the walls of every journalism school in America. It is the salient lesson of the Gary Webb affair. It might have saved his journalism career, though it would have precluded his canonization in the new film “Kill the Messenger.”

The Hollywood version of his story — a truth-teller persecuted by the cowardly and craven mainstream media — is pure fiction. But Webb was a real person who wrote a real story, a three-part series called “Dark Alliance,” in August 1996 for the San Jose Mercury News, one of the flagship newspapers of the then-mighty Knight Ridder chain. Webb’s story made the extraordinary claim that the Central Intelligence Agency was responsible for the crack cocaine epidemic in America. What he lacked was the extraordinary proof. But at first, the claim was enough. Webb’s story became notable as the first major journalism cause celebre on the newly emerging Internet. The black community roiled in anger at the supposed CIA perfidy.

Then it all began to come apart. The New York Times, The Washington Post and the Los Angeles Times, in a rare show of unanimity, all wrote major pieces knocking the story down for its overblown claims and undernourished reporting.

Gradually, the Mercury News backed away from Webb’s scoop. The paper transferred him to its Cupertino bureau and did an internal review of his facts and his methods. Jerry Ceppos, the Mercury News’s executive editor, wrote a piece concluding that the story did not meet the newspaper’s standards — a courageous stance, I thought. “We oversimplified the complex issue of how the crack epidemic in America grew,” Ceppos wrote. “Through imprecise language and graphics, we created impressions that were open to misinterpretation.”

Jeremy Renner plays Gary Webb in “Kill the Messenger.” (Chuck Zlotnick/Focus Features)

Webb resigned and wrote a book defending his reporting. The mainstream press, now known as the legacy media, which had vilified him and which he had vilified in turn, never employed him again. He worked as an investigator for a legislative committee in California and finally for an alternative weekly in Sacramento. He had money troubles and other problems, and ended up taking his own life at 49 in December 2004.

I had a ringside seat to the Webb saga. As an investigative reporter covering the drug trade for the Miami Herald, also a Knight Ridder newspaper, I wrote about the explosion of cocaine in America in the 1980s and 1990s, and the role of Colombia’s Medellin Cartel in fueling it.

Beginning in 1985, journalists started pursuing tips about the CIA’s role in the drug trade. Was the agency allowing cocaine to flow into the United States as a means to fund its secret war supporting the contra rebels in Nicaragua? Many journalists, including me, chased that story from different angles, but the extraordinary proof was always lacking.

Finally, in April 1989, the U.S. Senate subcommittee on terrorism, narcotics and international operations, chaired by Sen. John Kerry (D-Mass.), weighed in. After an exhaustive three-year investigation, the committee’s report concluded that CIA officials were aware of the smuggling activities of some of their charges who supported the contras, but it stopped short of implicating the agency directly in drug dealing.

That seemed to be the final word on the matter. And then Gary Webb came along.

I was in the Miami Herald’s newsroom when the rumble came across that the Mercury News had finally nailed the CIA-cocaine story, proving that the CIA was involved in the cocaine trade and, more significantly, that the agency was responsible for the U.S. crack epidemic. I was astonished — and envious. Until I read Webb’s story.

The first thing I looked for was the amount of cocaine that the story said “the CIA’s army” had brought into the country and funneled into the crack trade. It turned out to be relatively small: a ton in 1981, 100 kilos a week by the mid-1980s, nowhere near enough to flood the country with crack.

I was also eager to see exactly how he linked the CIA to the cocaine trafficking. (The online presentation of the articles memorably showed a crack pipe superimposed on the agency’s seal.) Was he talking about CIA officers, who are employees of the agency, or CIA agents, who are hired foreign contractors? Or subcontractors? Did he name or quote any of them? Did he have any documents?

What he had was this: the testimony of Oscar Danilo Blandon Reyes, described as a former contra leader and drug dealer. Blandon claimed that the leader of his contra group, who was on the CIA payroll, had said, “The ends justify the means.” In Blandon’s words, “So we started raising money for the contra revolution.” Blandon’s lawyer told Webb: “Was he involved with the CIA? Probably.”

Webb also wrote that Blandon’s boss had been accused by a witness at his Nicaragua drug trial of participating in a drug ring that flew cocaine into a U.S. Air Force base in Texas, though the base was not named.

There was no response from the CIA in the story. But the claims Gary made, man, were they extraordinary:

“For the better part of a decade, a San Francisco Bay Area drug ring sold tons of cocaine to the Crips and Bloods street gangs of Los Angeles and funneled millions in drug profits to a Latin American guerrilla army run by the U.S. Central Intelligence Agency, a Mercury News investigation has found.

“This drug network opened the first pipeline between Colombia’s cocaine cartels and the black neighborhoods of Los Angeles, a city now known as the ‘crack’ capital of the world. The cocaine that flooded in helped spark a crack explosion in urban America and provided the cash and connections needed for L.A.’s gangs to buy automatic weapons.”

And this: “Thousands of young black men are serving long prison sentences for selling cocaine — a drug that was virtually unobtainable in black neighborhoods before members of the CIA’s army started bringing it into South-Central in the 1980s at bargain-basement prices.”

In the business, these are called nut graphs, and they are the hardest things for an investigative reporter to write. You must summarize the sometimes bewildering facts you have uncovered, however incomplete or contradictory, and synthesize them into a picture that makes sense. That is what Webb did. And he went too far.

As the Mercury News was first coming under criticism for his reporting, and while the story was the hottest one in the country, an appeal went out to other Knight Ridder newspapers to pick up his journalism. I was asked to evaluate his reporting for my bosses at the Herald. The Herald did not publish Webb’s work.

After Webb was transferred to Cupertino, I debated him at a conference of the Investigative Reporters and Editors organization in Phoenix in June 1997. He was preternaturally calm. While investigative journalists are usually bundles of insecurities and questions and skepticism, he brushed off any criticism and admitted no error. When asked how I felt about it all, I said I felt sorry for him. I still feel that way.

Webb’s supporters point to a 1998 report by CIA Inspector General Frederick Hitz as vindication, because it uncovered an agency mind-set of indifference to drug-smuggling allegations. Actually, it is more like the Kerry committee’s report on steroids: “We have found no evidence in the course of this lengthy investigation of any conspiracy by CIA or its employees to bring drugs into the United States,” Hitz said. “. . . There are instances where CIA did not, in an expeditious or consistent fashion, cut off relationships with individuals supporting the Contra program who were alleged to have engaged in drug trafficking activity or take action to resolve the allegations.”

Significantly, the report found no CIA relationship with the drug ring Webb had written about.

Webb could draw a Pyrrhic victory from Hitz’s report. His work and the controversy it engendered forced the CIA to undertake one of the most extensive internal investigations in its history. Jack Blum, the special counsel who led the investigation for the Kerry committee, said after Webb’s death that even though Webb got many of the details “completely wrong,” he had at least succeeded in focusing attention on the issue.

But investigative reporting is unforgiving to those who get it only partially right, especially on their core claims. When a story gets that big, it invites scrutiny and criticism. And criticism of the criticism. Where does it all land in the end? The criticism of the criticism usually fails to come to grips with the salient point: No matter what you think of the CIA, there’s no putting the crack-epidemic genie back in the bottle.

You don’t have to believe me or Ceppos, or anybody else from the mainstream media on this one. These are the words of Nick Schou, the OC Weekly editor who wrote the book that serves as the basis, with Webb’s book, for the movie: “ ‘Dark Alliance’ contained major flaws of hyperbole that were both encouraged and ignored by his editors, who saw the story as a chance to win a Pulitzer Prize,” Schou wrote in the Los Angeles Times in 2006. On the crack explosion claim: “The story offered no evidence to support such sweeping conclusions, a fatal error that would ultimately destroy Webb, if not his editors.”

Despite his facade of certainty, Webb must have known this better than anyone. In his book he took pains to distance himself from the crack claim. “I never believed, and never wrote, that there was a grand CIA conspiracy behind the crack plague,” he wrote. “. . . The CIA couldn’t even mine a harbor without getting its trench coat stuck in its fly.”

Webb also admitted to mistakes in the execution of the story — though he put the blame on his editors, who he said requested “an increased emphasis on CIA involvement.” He said he rewrote those nut graphs at their insistence.

As for “Kill the Messenger,” the best that can be said for the movie is that Jeremy Renner gives a spirited performance in a fantasy version of the story in which everyone is wrong but Gary Webb. It would take an article longer than this one to point out the many departures from what really happened.

Webb will be lionized by some, and the simple story will get told and retold that the mainstream press and his management betrayed him, threw him under the bus. Many people will believe it. Hollywood was making movies about U.S. government cocaine trafficking as early as 1988. Go ahead and rent “The Last of the Finest” or “Above the Law,” if you can find them on Netflix. In the age of waterboarding and Edward Snowden, widespread CIA cocaine trafficking seems not only plausible but downright antiquated.

Before seeing the movie this past week, I hadn’t thought much about Webb in a long time. Mostly, he stands out in my mind as a cautionary tale, a warning, especially for the younger reporters on my staff, to keep the hype out of their nut graphs.

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