Question: was blood in blood out a true story

Answer: No, The three prison gangs in the film are fictional creations of screenwriter Jimmy Santiago Baca and director Taylor Hackford. However, they were all loosely based on actual prison gangs, with the Aryan Vanguard, Black Guerrilla Army and La Onda representing the Aryan Brotherhood, Black Guerrilla Family, and the Mexican Mafia, respectively.