Brody and Stone (1989) list other forms of monitoring. One technique is to have the monitors look for a trigger event, which is an event or activity that might focus public concern on a topic or issue. For example, the Exxon Valdez oil spill in Alaska brought heavy visibility to environmental concerns, and the Columbine High School tragedy sparked interest in school safety and teen age alienation, However, there is no scientific way to determine what is or what may become a trigger event. Monitors are left to trust their instincts and judgment.