I agree with your point that CNN’s article didn’t specifically express that tattoos were key in identifying gangs and gang members, however the claim that tattoos are used as identifiers is not wrong. Unless your claim was that this specific article did not say that, you would be wrong, as multiple reports with El Salvadorian prison guards and staff members have claimed using tattoos as markers for gang members. Also, the link attached was to a tweet of a video where they were specifically stating that tattoos were markers. So again, in reference to specifically the article you would be correct, but to the claim, you would be incorrect.