Key witness Chris Serino, the Sanford (Fla.) Police Department’s lead investigator in the 2012 shooting death of 17-year-old Trayvon Martin , began his testimony in the George Zimmerman murder trial Monday afternoon.
Serino, the 25th witness called by the state, is expected to testify about how he called the events that unfolded the night of Feb. 26, 2012, "avoidable." He also interviewed Zimmerman in the aftermath of the shooting.