He was indicted last week on four felony charges. A grand jury believes he illegally deployed on-duty deputies and couldn't account for thousands in charity and campaign cash.
Latino civic leaders say the district attorney was racially motivated in charging Trevino, and not other constables.
"We question the process and the timing of the indictment," said Johnny Mata with LULAC. "We are used to kangaroo courts and injustice being committed every day against people of color."
"It seems there is not equality and there's not consistency in how the DA picks who they are going to do," said activist Beverly Covalt.
"Regardless of what happened with other constables, should Constable Trevino have to answer for what happened?" we asked Covalt.
"Of course," she answered. "But there is a process and we're saying not everyone follows is made to adhere to the process."
The district attorney's office did not respond, except to say it will not try this case in the media. Trevino plans to fight the charges. Friday's news conference was, at times, contentious.