A motorist whose Tesla was in self-driving mode slammed into a California police car while the officer was investigating a separate, deadly crash. The crash is the latest in a series of accidents to have weighed on the closely watched development of driverless mobility, and self-driving rivals Waymo and Cruise have also experienced mishaps. Proponents of self-driving cars say they will ultimately be safer than human drivers, yet the high-profile crashes have done little to help build trust in this emerging technology. The latest incident happened early Thursday in Fullerton, about 25 miles sou…