Extradited in 2017 after escaping twice from Mexican prisons, Guzman is serving a life sentence at a maximum security facility in Colorado on multiple charges including drug trafficking and money laundering.

AFP consulted three letters the co-founder of the Sinaloa cartel wrote, each one filed on Monday.

“This is a polite letter (about) the hardcore evidence that wasn’t proven for my case,” Guzman wrote in English.

In the letter directed to the Eastern District Court of New York, Guzman asked that authorities recognise his “rights to be request back (sic) to my country,” without clarifying if his request is to serve the rest of his sentence in Mexico.

In another missive on April 20, Guzman complained that his requests for the documents behind his sentencing have gone unanswered.

These documents won’t justify “my cruel punishment,” he added. “The verdict of my trial wasn’t fair,” he said.

El Chapo said that he has been waiting for an appeal for three years, and invoked the protection of the “first to the fifth amendment.”

The former trafficker has repeatedly complained in previous prison letters of isolation, poor conditions in his cell and the lack of family visits.