SAN DIEGO — In a decision that bolsters the police use of streetlight cameras as investigative tools, a state appellate court upheld a San Diego murder conviction in a case solved by using the footage, finding that the defendant did not have an expectation of privacy when he moved about on a downtown street. The case, the 2019 slaying of a business owner gunned down during a robbery, was also among the first times that San Diego police had used footage from streetlight cameras in an investigation. Police gleaned the license plate of the suspected killer, a man who wore a Halloween mask with th…