NFL game officials will not be responsible for identifying gang signals but will alert league headquarters of anything unusual or suspicious they see. League executives declined to outline what action might be taken against offenders, but Pereira said, "it will be dealt with harshly. The commissioner is not going to stand for gang signals on the field."
Ahlerich does not believe the problem to be widespread in the NFL but says the league has spoken to some players about their use of hand signals. He declined to identify the players.
First-year players were counseled on the matter at the recent rookie symposium, and last year a video on the dangers of gangs was required viewing for every player in the league.
The way some players see it, there is guesswork involved, even for the experts who are studying game video.
"Guys come from all over the country, and who knows what they're really doing?" said Jacksonville Jaguars receiver Dennis Northcutt, adding he cannot remember seeing a gang gesture in his nine NFL seasons. "People have got signs for their kids, signs for their fraternities. How do you differentiate who's really throwing up gang signs?"
Northcutt gave an example.
"This is a gang sign," he said, touching his index finger to his thumb to form a squished OK sign. "But at the same time, it's a sign for a personnel group."
Pereira said the gang experts take those factors into account and are very thorough when investigating gestures that appear suspicious. They are on the lookout for "symbols, clothing, jewelry or other items that would signify an association with criminal gang enterprises," Ahlerich said.
That's not unique to the NFL and NBA, nor is it limited to professional sports.
In an e-mail, NHL spokesman Frank Brown said Tuesday his league has "a general prohibition of profane, vulgar or inappropriate gestures (i.e., the throat slash). I am not aware of there ever having been reason to employ a gang expert."
Major League Baseball doesn't study game video, but it does have a policy legislating merchandise. About a year ago, at the insistence of baseball and the New York Yankees, apparel-maker New Era pulled from the shelves Yankees' caps featuring the team's insignia emblazoned with gang colors and logos.
In college sports, the Pacific 10 Conference in 1992 instituted a rule prohibiting football players from wearing bandannas, allowing them to wear elastic skullcaps only if they were in the school's primary colors or black.
