DEA agents with captured Zetas leader Osiel Cardenas

A newspaper in Mexico has revealed US officials met with members of Mexican cartels throughout the past decade, a little reported but common tactic as authorities seek to identify and isolate targets in the "war on drugs."

As part of the El Universal investigation, the newspaper obtained legal documents from both US and Mexican agencies that proved agents from the US Drug Enforcement Administration (DEA) and investigators from the Justice Department met with members of various Mexican cartels in an attempt to gather information on their rivals.

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According to the investigation, the US government was aware of the meetings, while Mexican agencies which knew about them made no attempts to inform the country's Congress. The documents showed that US officials established a network of informants in the cartels and passed on information to Mexican authorities, which used it to carry out anti-drug operations without revealing how they were made aware of the people or drugs they targeted.

As well as highlighting meetings between the DEA and members of the Gulf Cartel between 2009 and 2011 -- part of efforts to combat the Zetas when they were at the height of their expansive power -- the documents demonstrated that meetings had taken place between the DEA and Vicente Zambada -- the son of Sinaloa Cartel boss Ismael Zambada -- who is currently awaiting trial on drugs charges in Chicago and has claimed as part of his defense that he had immunity.

InSight Crime Analysis

The detailed revelations show the US continues to work with criminal elements as part of antinarcotics efforts. This is not some conspiracy to protect or favor certain groups -- it is a tactic employed by the DEA and other US agencies to allow them to focus efforts on priority targets, and allow them to build solid cases. A prime example can be seen during the hunt for Pablo Escobar, when there was contact between US agents and Diego Murillo, alias Don Berna -- among other criminals -- who would himself later rise to lead the Medellin underworld. Murillo was eventually captured and extradited to the United States, where he is currently serving a long-term sentence for drug trafficking and money laundering.

As the case of Murillo demonstrates, collaboration with US authorities does not preclude informants later becoming a law enforcement target -- so the fact Vicente Zambada is known to have spoken with US agents does not offer weight to claims by his defense that he was immune from prosecution. It also means that, if US operational focus has at time favored one cartel over another, it can quickly shift, making former collaborators the new priority.