Some signs your child might be involved with a Latino gang are the choice of hat or belt buckle he wears, even his favorite number, a gang expert told a Spanish-speaking audience in southeastern San Diego on Tuesday.

"The number 13 is super important," San Diego police officer Carmelin Rivera said. It stands for the 13th letter of the alphabet, the letter M, the symbol for the Mexican Mafia prison gang, he said.

The Mexican Mafia controls Mexican gangs in Southern California, he said.

"Only gangs can use that number, have the tattoo, or use it to tag," he said.

Rivera gave his primer to gangs to an audience of 60 mostly Latino parents at a town hall meeting on public safety hosted by the FBI and San Diego police at the Jacobs Center.

While overall crime in San Diego is down, gang violence is up this year, according to police. At least six gang-related murders have occurred this year, compared to four all of 2010, police said. The most troubled neighborhoods in the city are in southeastern San Diego.

David Garcia, coordinator of the neighborhood safety group Project Safe Way, called the Spanish-language forum "groundbreaking" because it was done without translators.

"When you use earphones you lose a lot in the translation. When you hear it in Spanish it hits you directly. The 60 people here understood everything. You know they understood because they were asking questions."

Audience members asked questions but mostly listened to the presentations about gangs, crimes against children and identity theft.

Rivera said San Diego has about 90 gangs made up of different racial and ethnic groups and more than 4,200 documented gang members and "hundreds more" who want to be part of that criminal lifestyle.

He urged parents to get involved with their children, keep an eye on who they hang out with, what they wear and even the social network sites they visit on their computers.

He used a PowerPoint presentation to show gang writing and wear, including baseball caps that Latino, Asian and black gang members like to wear because of their letters.

The M on a Minnesota Twins baseball cap could mean he identifies with the Market Street gang, he said. The P on a Pittsburgh Pirates cap could mean it's the Paradise Hills Locos, he said. The J on the Toronto Blue Jays cap is for a gang called J Block near 35th and Market streets.

A belt buckle with the letter L could stand for the Linda Vista gang, an S could be for Shelltown or Sherman Heights or Southeast San Diego gangs, an E for Eastside San Diego.

"If you see your children have something like this, it's not because they like that letter, it means they are trying to be with a gang," he said. "They are trying to identify themselves with a gang."

"It's difficult as a parent to accept that your child is involved with gang," he said, "but it's super important that you investigate, that you ask questions."

Leonel.sanchez@sandiegored.com