(Reuters) - San Francisco prosecutors will study all criminal investigations conducted over the past 10 years in light of an inquiry into racist and homophobic text messages allegedly sent by four police officers, District Attorney George Gascón said Monday. The text messages came to light as part of the corruption case against a fifth officer, whose own text messages were submitted in court last week. "In order to ensure our criminal justice system is fair and equitable, my office is conducting an immediate assessment of every prosecution within the past 10 years where these officers were involved," Gascón said.