Mendota MS-13 investigation relied on Facebook Messenger until news report

FRESNO, Calif. (KFSN) -- Action News has uncovered some of the evidence used to arrest MS-13 gang members accused of operating a ring of violence, drugs, and fear in the Mendota area.

The charges range from murder to conspiracy to drug trafficking and they're filed in both federal and state court. Court documents reveal investigators found a lot of the best evidence in conversations on Facebook.

Mendota has lived in fear of MS-13 for years, but its residents may finally be breathing a sigh of relief.

Accused gang members went to court Wednesday to face charges for years of criminal activity.

Prosecutors charged more than 20 people with some of them facing felonies in both federal and state court.

"Then it becomes a procedural nightmare as to how you're going to handle these types of cases," said legal analyst Tony Capozzi.

For now, the federal cases are taking the priority and one of the main targets is a guy known as a gang leader -- someone who's killed at least three people who calls the shots for underlings now.

The federal complaint charges him with assault and outlines how investigators used Facebook Messenger to corroborate video evidence of the attack.

"My goodness, the plethora of information corroborating everything that happened," Capozzi said. "Conversations between the defendants on what to say, what not to say. 'Don't snitch on me. Don't say this. Don't say that.' It's just devastating what it's done to the defense in this case."

Three weeks ago, Reuters reported that the FBI investigation tried to get even deeper, getting a judge to sign off on essentially a wiretap for voice conversations over Messenger.

Facebook pushed back, saying its software isn't currently designed to do that.

Until then, the entire operation was under seal, and Capozzi says the report may have changed the course of the investigation.

"If that hadn't happened, this case might still be going on in terms of investigation and they might've brought more people into the fold," he said.

Only four of the defendants appeared in the Fresno County courthouse Wednesday.

The rest of them are in federal custody and for now, only their federal cases will move forward, even though the Fresno County district attorney charged at least ten of them with murder or a murder conspiracy.