Factual error: The film implies that Ned Kelly and his friends only became criminals after being harassed by the police. In fact, they had a long history of criminality, bushranging and animal rustling before being declared outlaws.
Factual error: The Los Angeles Police Department no longer has an Internal Affairs division. The division is known as the Bureau of Professional Standards and is subject to civilian oversight - meaning the roughshod treatment Gavilan was receiving at their hands would have been checked at minimum by a civilian review board. That having been said, Gavilan's behavior should have gotten him in trouble regardless of whether or not someone in the department was out to get him.
Factual error: When Stanley runs after Zero who is lost and finds him passed out, Zero offers Stanley "sploosh" which we deduce is rotten peaches from Sam's boat which they are taking shelter in. Had the peaches survived both the descent to the bottom of the lake after Sam was killed AND the effects of time, they would be extremely fermented and would be alcoholic. Stanley and especially Zero, would be drunk and would surely dehydrate to death or at least not be able to climb "God's Thumb" coherently.