LOS ANGELES — When Kathryn Steinle was killed in July 2015 while strolling with her father on a San Francisco pier, Donald J. Trump’s campaign was just two weeks old.

For the next 16 months, he seized on the killing as an example of the problems with illegal immigration and sanctuary cities. The man who fired the gun, Jose Ines Garcia Zarate, was an undocumented immigrant who had been deported several times and had recently been freed by the San Francisco County sheriff.

Even amid the drumbeat of outrage from Mr. Trump and other Republicans over Ms. Steinle’s death — and now, Mr. Garcia Zarate’s acquittal on Thursday of murder — San Francisco and the rest of California have not taken a harder line against undocumented immigrants.