The protesters were careful to note they did not condone Christopher Dorner's actions -- he is suspected of killing four people in a days-long rampage triggered because he was fired from the department, he says because of his race.
Those expressing support for Dorner Saturday, though, said they believed police were out to kill him and ignored the rule of law in the process.
Officers twice fired at vehicles mistakenly believing Dorner was inside. One woman is still recovering from a gunshot wound in the back, the Los Angeles Times said Sunday.
Michael Nam, 30, one of the protesters, carried a sign made to look like a tombstone, with the inscription "RIP Habeas Corpus."
"How the police handled this -- they were the judge, the jury and the executioner," Nam said. "As an American citizen, you have the right to a trial and due process by law."
Others at the protest said they believed Dorner was fired because he was black and said they wanted to set the record straight on why he was let go.
Police said he falsely reported a training officer kicked a man in the head, which was the reason for his termination.
Law enforcement officials defended their handling of the manhunt, noting it was their own officers who were being targeted.
San Bernardino County Sheriff John McMahon defended his department's conduct, saying Dorner killed one of his officers and wounded another.
"The bottom line is the deputy sheriffs of this department, and the law enforcement officers from the surrounding area, did an outstanding job," he said. "They ran into the line of fire."