Homero Zamorano Jr., 47, of Pasadena, Texas, faces four counts along with his alleged accomplice, Christian Martinez. The defendants have until June 15 to reach a plea agreement, otherwise the case will go to trial.

In total, 53 people, from Guatemala, Honduras and Mexico, died from high temperatures and lack of oxygen inside the container. The truck had left Laredo at about 2:45 p.m. and traveled 146 miles to San Antonio, passing through a Border Patrol checkpoint undetected.