Where an understanding of gang etiquette is required to explain the prosecution’s theory of the case, an explanation of such is permitted and considered more probative than prejudicial so long as the remarks remain reasonable and appropriate.The 1st District Appellate Court affirmed the decision of Cook County Circuit Judge Matthew E. Coghlan.At midnight on May 29, 2010, two groups of men belonging to rival gangs got into conflict. One man, Alan Oliva, was beaten to death, and a man who escaped the fight identified Daniel …