About 50 protesters marched in downtown Los Angeles on Saturday to decry violence by illegal immigrants and to demand that the Los Angeles Police Department change its controversial policy limiting when someone can be questioned about their immigration status. The marchers, including anti-illegal-immigration Minutemen and local community activists, also called for justice for Jamiel Shaw II, 17, a black athlete who was shot and killed in March by an alleged gang member who was in the country illegally.