A brand new theory offers an answer to the infuriating question of why a criminal group in Mexico murdered dozens of protesting students last year in Guerrero, but the lack of supporting evidence limits the chances that it will offer any closure to this tragic episode.

Last month, the Interdisciplinary Group of Independent Experts (known as the GIEI, for its initials in Spanish) — an ad-hoc investigative coalition of investigators convened to conduct an inquiry into the 2014 disappearance of 43 student protesters in Iguala, Mexico — presented their final report. 

The 560-page document serves as a comprehensive condemnation of the slipshod government response, replete with overlooked contradictions and unsupported conclusions. The evidence driving the government’s conclusion that the students were abducted for interrupting a speech by Iguala first lady Maria de los Angeles Villa Pineda is weak. Weaker still is the government’s conclusion that the students were incinerated in a local dump. Shining the spotlight on the government’s incompetence is the chief contribution of the GIEI report, which will hopefully serve as both a model for future investigations and a cautionary tale against similar smokescreens in the future. 

The 560-page document serves as a comprehensive condemnation of the slipshod government response, replete with overlooked contradictions and unsupported conclusions.

The report also posits an alternative theory for the motivation behind the attack, a question that has plagued analysts and investigators since the incident. While the report’s authors do not make any conclusive finding, they suggest that one of the five busses commandeered by the students prior to their disappearance was loaded with heroin headed for the United States. At that point, the Guerreros Unidos, the local gang allegedly behind the massacre, would have an obvious business motivation for getting involved in what was until then a routine political dispute. Moreover, they weren’t certain which of the busses it was, which required them to attack and retake all five of them.

There are a number of elements of the Iguala case that are consistent with this hypothesis. One is the highly coordinated monitoring of the students’ activities by representatives from several different federal and municipal agencies. This also appears to be anomalous and could stem from their collusion with the Guerreros Unidos, and their consequent interest in the destiny of a heroin-laden bus. 

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Another element is the December 2014 indictment of several Chicago-based members of Guerreros Unidos by the US attorney in Chicago. The case filings include affidavits from DEA agents that detail the smuggling tactics employed by the gang, including the use of commercial busses (like those the students took) from drug-producing areas in southern Mexico to complete portions of the journey. 

The hypothesis also feeds the palpable desire to settle on an explanation for what is such a bizarre and meaningless mass killing.

The centrality of the bus to the attack’s motivation would also explain the government’s particular fumbling in its account of the busses that the students commandeered. Government investigators accused the students of abandoning and destroying one bus, but without providing any evidence of this destruction and ignoring evidence to the contrary. The GIEI concluded that the government simply fabricated the story out of thin air. When the GIEI requested the opportunity to review another bus seen in security footage, Mexico’s attorney general’s office handed over a bus that was demonstrably different. 

There is a certain plausibility to this theory, which has garnered attention from international media outlets. The hypothesis also feeds the palpable desire to settle on an explanation for what is such a bizarre and meaningless mass killing. But there are substantial flaws to the GIEI theory: the logic is incredibly thin, and not without its own set of holes, and the evidence is all but nonexistent. 

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Many of the problems start with a more detailed look at the Chicago case filings, in which there is nothing more than a circumstantial link to the Iguala case. As the GIEI authors acknowledge, the bus companies that, according to US authorities, the Guerreros used to transport heroin did not include Estrella de Oro, the transportation company that owned the vehicle abducted by the students and suspected of carrying the heroin shipment.

It is also striking that the US authorities would have failed to make the connection between their suspects and the Mexico disappearance. Given the amount of attention on the Iguala disappearances and their own personal interest in the gang alleged to be the perpetrator, the DEA agents and prosecutors who made the case were surely aware of the missing students. Tying their suspects to such a notorious crime would seem an obvious move for them, guaranteeing the case a substantial amount of attention. The US investigation surveilled the targets, including the use of telephone wiretaps in which the suspects incriminated themselves, through November 2014, meaning that the investigation coincided with the Iguala disappearances. At some point, someone involved in the US case would likely have made the connection, if there was one to make.

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To give the new theory more weight, one would expect to see corroboration from some suspect (many of whom have spoken at length about the incident) or some other direct piece of evidence. Without that, all that really ties the theory together is the Guerreros’ use of busses (a relatively common practice and a likely coincidence) and the government’s bungling of the inquiry into the busses’ role (which seems less significant when one considers that the government bungled virtually every element of the investigation). We are left, then, without any non-circumstantial basis for this theory.

Correct or not, without any further substantiation, the GIEI theory is simply another possible answer to a riddle that has already spawned dozens of conspiracy theories.

The heroin bus theory also fails to fully explain the motive. It would explain the gang’s interest in the busses seized by the students, but even if we ignore the evidentiary shortcomings and accept this version, it remains unclear why they saw it as being in their interest to abduct and likely murder the students. It would have presumably been possible to stop the bus, recover the drugs, and then send the protesters on their way without committing a massacre that would draw a flood of federal and international resources on the Guerreros. Why gang-leaders did not opt for this approach remains as unclear today as ever.

None of this is to demonize the GIEI, whose report deserves the plaudits it has received. Moreover, the group is merely offering a possibility rather than a conclusive statement, and the heroin-in-the-bus theory is as good as any of the others floating around the Iguala debate. 

But it does mean that we are no closer to answering a central question behind this episode. Correct or not, without any further substantiation, the GIEI theory is simply another possible answer to a riddle that has already spawned dozens of conspiracy theories.