DURING my many years as a correspondent in Mexico, some of my best reporting happened around dinner tables. So on a recent trip back, I dined with a range of old contacts to catch up on how Mexico was handling its most pressing challenges, like the 2014 student massacre in southern Mexico, which shocked the world and ignited protests across the country.

But all anyone wanted to talk about was Donald Trump.

My dinner companions were not alone in their fixation. About a week later, the Mexican government announced that it was shaking up its diplomatic corps to address the anti-Mexico rhetoric spewing from the Trump campaign, which a Mexican official told The Washington Post threatened to “damage the image of Mexico in the United States.”

On Sunday, however, Mexico showed that the deeper damage to the country’s image is self-inflicted.

An independent investigative panel released its final report on the massacre in the state of Guerrero, which left 43 students of a rural teachers college in Ayotzinapa missing and presumed dead. Its findings were devastating.

The Interdisciplinary Group of Independent Experts, whose work has led to high-profile prosecutions against the Colombian military, a Guatemalan dictator and American oil companies, not only provided the most chilling account of what the students had suffered one night in September 2014, but it also showed that the Mexican government had, at the very least, badly mishandled the investigation, and quite possibly attempted a cover-up.