Four men were convicted Thursday in last year's killing of 15 people at a teen party in the border city of Ciudad Juarez.
A three-judge panel delivered guilty verdicts on several counts after a two-week trial in Juarez, which in recent years has been the deadliest zone in Mexico amid spiraling drug violence.
President Felipe Calderon set off national outrage when he referred to the victims of the Jan. 30, 2010, massacre as gang members. He backpedaled after it turned out they were promising students and athletes.
The attack remains one of the most horrifying episodes since Calderon launched a government offensive against drug cartels in December 2006. About 40,000 people have been killed in drug-related violence in Mexico since then.
During the trial, the judges weighed forensic evidence and heard statements from 17 protected witnesses who testified behind closed doors and via videoconference.
Jose Dolores Arroyo Chavarria, Aldo Flavio Hernandez Lozano, Juan Alfredo Soto Arias and Heriberto Martinez were found guilty of murder, attempted murder, arms possession and criminal association. They are to be sentenced Monday, and prosecutors said they will seek terms of more than 100 years.
Arroyo told authorities after his arrest in February 2010 that he served as lookout for two dozen gunmen who had been ordered to kill everyone at the party.
He also said the main Juarez-based cartel ordered the hit because members of a rival gang were reported to be in attendance.
Chihuahua is one of the first states in Mexico to implement open court trials, in which evidence is presented in public session and defense attorneys have the right to question witnesses.
Cecilia Sanchez of The Times' Mexico City bureau contributed to this report.