This appears to be a nationwide problem. In May 2012, the United States Department of Justice Civil Rights Division weighed in on the issue by publishing a letter to provide guidance to police departments as to the right to (and importance of) photographing police brutality under the First Amendment and the impermissibility of warrantless police seizure of resulting images under the Fourth and Fourteenth Amendments.
The case of Christopher Sharp v. Baltimore City Police Department arose after cops demanded a man's cell phone he used to record cops forcibly arresting his friend. When the cops returned the cell phone, the images of police brutality had been deleted along with other personal photos with sentimental value. DOJ Civil Rights Division filed a statement of interest in the case and later issued a letter to provide policy guidance.
The DOJ letter in Christopher Sharp v. Baltimore City Police Department makes clear that the First Amendment protects the right of citizens to record police officers in discharge of their public duties, including when they abuse power, and to disseminate images of such power abuse as a means of criticism in a peaceful manner.
The letter also clarifies that the Fourth Amendment (of heightened importance in the First Amendment context) and the Fourteenth Amendment prohibit seizure of cell phones used in photographing police brutality absent a warrant or exigent circumstances, as well as prohibit the destruction of resulting images without requite due process.
"These rights," the letter begins, "subject to narrowly-defined restrictions, engender public confidence in our police departments, promote public access to information necessary to hold our governmental officers accountable, and ensure public and officer safety."
Presumably, the content of the letter as well as the related statement of interest may also help defeat claims of qualified immunity and lack of Monell liability for police officers and departments that violate the rights of citizen journalists engaged in photographing police brutality in California.