When Philando Castile was shot by a Minnesota police officer, his girlfriend broadcast his final moments live on Facebook. But experts say the footage from a squad car camera was probably a bigger factor in prosecutors’ decision to charge the officer with manslaughter. And that footage, which has not been made public, is still no guarantee that Jeronimo Yanez will be convicted, as other police shootings have shown. “There have been cases that had video that resulted in either an acquittal or a hung jury, so sometimes the video may raise more questions,” said Philip Stinson, a criminologist at Bowling...