One of the many predicted benefits of regulating marijuana is to allow police to focus on solving violent crimes, and an investigation into the Oakland Police Department shows just how imperative that focus is. In 2012, OPD solved only 28% of homicides, a figure that is largely due to an incredible backup of untested evidence.  The OPD’s crime lab has yet to test evidence pertaining to 659 homicide cases, some of which are 10 years old. Furthermore, the crime lab has no idea which of the cases with…