In downtown San Francisco, there is a private security guard and a San Francisco police officer on duty at every store.
But this is what happens. I have witnessed it myself.
The private security guard will point out a thief to the copper. The copper will then make the thief empty his bag of the shoplifted goods and then send him on his way. No arrest made.
Under California law, theft under $950 is considered only a misdemeanor, but many prosecutors throughout the state have opted to free those charged with the offense under certain conditions rather than holding them in jail for the maximum sentence of six months.