The issue I have with John Oliver's piece is that he starts immediately by claiming that the robbery video has absolutely nothing to do with what happened afterwards and should not be taken into account.
The video doesn't have anything to do with the incident in question. And it is relatively improper for the police to release a video that is not related to this incident, as it does nothing but expose potential jurors to evidence that could otherwise be excluded in a criminal or civil trial.
The only potential relation that the video would have to this incident is in regard to Mike Brown's state of mind, and again, that's for a court of law to determine, not for the police department to prematurely release in a response to this incident, not in response to questions about the robbery.
He then goes on use clip after clip to portray the Ferguson police department in a bad light yet in a similar manner, none of which is relevant to the case. That inmate whose blood got onto a police officer's uniform? Irrelevant. How many blacks on the police force? Irrelevant.
True, but he's also using those clips in response to people saying there are no race issues in Ferguson. He never once stated that because cops have treated blacks poorly previously, then they did so in this case. He was making fun of the mayor for saying something that was patently false.
You can't use the robbery video as evidence to claim he would be violent with a cop but you could use the robbery video to say that his state of mind would influence him to be violent with a cop. Am I misunderstanding your point?
You can't bring in evidence of a separate incident in order to show that the person has a history of doing something. Just because I hit someone once before does not mean I will hit someone else in the future. It's prejudicial to try to paint me as a "habitual hitter" with a propensity to hit people just because it's happened previously. You judge an incident based on the facts involved in the incident, not facts from previous incidents. And before everyone starts arguing and whining about how unfair that is, I'm just pointing out what the rules of evidence state. You don't have to like it for it to be true.
However, if the previous incident of me hitting someone can somehow affect my state of mind in this instance, then it can be brought in. In Brown's case, he robbed a store and had not been confronted by police about it yet. Thus, it's reasonable to assume that if a police officer were to approach him, his state of mind would be that the officer was there to address the robbery.
If, on the other hand, Brown had robbed this store years ago, had been arrested, and had already served his sentence or had the charges dropped, then the robbery would be completely irrelevant to this case. It's not reasonable for Brown to assume that the police are there to ask him about a robbery that has already been addressed, so it's not reasonable to assume that his state of mind was affected by the previous robbery. A person's state of mind when the incident took place is relevant to the incident, and so evidence relating to his state of mind can be introduced, even if that evidence consists of prior acts.