A few days later, there was a small meeting between journalists and two of the experts, the Spaniard Carlos Beristain, a human-rights specialist in disappearances and victim trauma, and the Chilean Francisco Cox, an expert consulted by GIEI and a lawyer and specialist in criminal law and human-rights law. Beristain and Cox seemed a bit awed by what they had unleashed. From a conversation whose details were mostly off the record, I came away with the impression that they weren’t sure what to expect in the near future. It was generally assumed by journalists that there would be hard-liners in the government, including Murillo Karam loyalists, who would try to discredit the experts and the report and to defend the “Historical Truth” as far as they could. But Beristain and Cox seemed confident that there were at least some members of the government who were open to re-starting the criminal investigation. However, nobody seemed to know where President Enrique Peña Nieto and the government’s top powers stood, or whether they were united or divided about what to do.

It was at that meeting that I first heard the report described as “historic . . . unprecedented in Mexican history,” by the writer and journalist Juan Villoro. Over the coming days, as people began to read the five-hundred-page report and its import began to sink in, I heard other journalists describe it that way. The report was historic not just because it was the first time that the Mexican government had acquiesced to such an intrusion by foreigners on its authority but, I think, it was also the first time Mexicans had ever seen a real criminal investigation, conducted by independent and autonomous justice professionals rather than by those subservient to a possibly complicit government. But I also heard a journalist say at that meeting, and I later heard some others say it, that the report’s weak link was precisely the forensic report on the dump fire. That’s where, in the short term, the GIEI would be attacked, because it could be presented as just a matter of one scientist’s opinion versus that of the P.G.R.

That was indeed how the report was treated in much of the mainstream Mexican media, most of which faithfully try to represent the government’s point of view and to defend it. These news organizations depend on government leaks, and they reliably go on the offensive on the government’s behalf, commonly disparaging victims through innuendos and smears. They tried to portray the Ayotzinapa students, for example, as vandals, guerrillas, and even as narcos. The reliably pro-government newspaper Milenio provided a telling example of how the fire-forensics controversy could be spun; the writer and journalist Héctor Aguilar Camín noted that, after the GIEI presentation, another of the drug gang’s leaders, El Cabo Gil, had been arrested. According to the P.G.R.’s version, based largely on confessions by other captured gunmen, it was on El Cabo Gil’s orders that the students had been massacred and burned at the dump. Aguilar Camín wrote, “Science is not clearing up the doubts about the Ayotzinapa case. It’s increasing them. The P.G.R.’s experts insist that the bodies of the disappeared were burned in the Cocula dump. The fire expert for the independent commission who studied the case, José Luis Torero, says such a fire was impossible. . . . [T]he conclusions provided by the experts feed doubts, and return the case to the shadows and to whatever anyone chooses to believe. . . . Those who believe that the dump fire is scientifically impossible are required to doubt the confession of Gildardo López Astudillo, ‘El Cabo Gil’, who says that he ordered the normalistas to be killed and burned precisely in that spot.” He concluded, “The argument among the experts helps to consolidate Ayotzinapa as one more episode of that Mexican specialty of believing what you want to believe; in the end, that specialty is to not believe anything.”

Aguilar Camín’s opinion piece cleverly abets the idea of cynicism as an almost folkloric Mexican custom. He posits the P.G.R.’s scientists, unnamed employees of the National Autonomous University of Mexico’s biology department, as equal in expertise to the GIEI’s Torero, a world-renowned fire-forensics expert. That’s not a persuasive argument, but it’s permissible. But Aguilar Camín’s arguments also disregard the skepticism regarding the dump fire previously expressed by the Argentine forensic experts, as well as the results of another study, performed by a team of UNAM physicists, that reached conclusions similar to Torero’s.

And why shouldn’t one be skeptical of the statements of El Cabo Gil, the long-sought-after leader of the Guerreros Unidos, who was finally captured in nearby Taxco, Guerrero, on September 17th? The GIEI experts discovered and reported many instances in the P.G.R.’s case of confessions extracted through torture, threats, and other forms of abuse. If the Cocula dump scenario was an orchestrated fiction from the start—the science in the GIEI report implies such a conclusion—any confessions asserting otherwise are implicitly suspicious, especially given the forms of coercion that lie behind the profusion of contradictory and false evidence that the GIEI discovered and reported. The report especially exposes the wildly contradicting confessions of the other Guerreros Unidos gunmen, who said they’d participated, on El Cabo Gil’s orders, in the dump massacre and burning. For example, on Pages 133 and 134 of the report, there is a brief analysis of when the various Guerreros Unidos gunmen who confessed to the fire—thus far the P.G.R.’s central witnesses in the case—said they were ordered to Iguala by “Gil’s right-hand man,” in order to resist an incursion by a rival drug gang known as “los Rojos.” Three of the four men say they were summoned to Iguala between seven-thirty and eight-thirty, an hour of that night “when the normalistas hadn’t yet even entered the city.” It was not until eight-fifteen that the “five or seven” students had first boarded the Costa Line bus outside Iguala and ridden into the city with the driver to discharge his passengers, an event that would not have drawn any attention in itself. It wasn’t until the students were locked into that bus and summoned the students in the other two buses to the station—at least forty-five minutes later—that the night’s violent events were triggered.

Still, the media focus on the dump fire was drawing attention away from the rest of the report. And that report of a criminal investigation was unprecedented, certainly in modern Mexico, because there, within hundreds of pages, facts were objectively laid out so as to accumulate into a complex but coherent narrative of a complex crime. The report doesn’t jump to tendentious conclusions unsupported by its collected evidence, it doesn’t cover up or disregard key evidence, it doesn’t try to fortify its case by ignoring recurring and extreme contradictions in the statements of those so far arrested. And the report expresses due skepticism of testimonies extracted through abuse and torture—including, possibly, those of El Cabo Gil’s companions—of which the GIEI discovered and reported many instances.

Three weeks after the report was presented, on September 26th, the first anniversary of the tragedy, an easy-to-overlook footnote from its five hundred densely detailed pages provided new headlines, and added new urgency to the GIEI’s insistence on being permitted to interview members of the Mexican Army’s 27th Battalion. The footnote included the information that on that night, after the Ayotzinapa students had been detained, a second-in-command of the Cocula Municipal Police, César Nava González, asked a commander of the Iguala police, Francisco Valladares, where the youths were being taken: “to the 27th Battalion or to Cereso,”a local detention center? Nava had provided that brief account in his original statement to P.G.R. investigators, and the GIEI had discovered it, as they did so much else, embedded amid the vast volumes of the case files. A reporter for the online news site La Silla Rota wrote of that provocative nugget of information, “It might have been just a baseless question, or it might reveal a manner of operating and coordinating between municipal police and elements of the Mexican Army.” Nava González, the reporter wrote, was a former member of the 27th Battalion, as were several others among the local municipal police forces; they had deserted. The fugitive former chief of the Iguala police also had served in that battalion.