But thanks in part to bystanders who captured video of this teen's encounter with police, Judge Diana Stuart acquitted him last week. After being illegally stopped, her ruling acknowledged, the youth did tense his arms, struggle to stay on his feet, and flail around with his limbs. But he did so to protect himself from "senseless and aggressive" violence that "a reasonable person would have felt was excessive force," she found, adding that police misrepresented parts of the encounter in their report, which she did not find credible after reviewing the video evidence.

Cases like this are thorny.

In the course of their jobs police will sometimes make understandable mistakes that cause them to detain or arrest an innocent person, and it is untenable to grant everyone a right to fight back against the cops at the moment of an arrest. At the same time, when police descend upon an innocent who is doing nothing wrong, roughly grab him, and react to his understandable confusion, alarm, and tensing of arms by punching, pummeling, and even tasing him, it's easy to see how that individual might start to feel like he's not "resisting" so much as protecting himself from bodily harm being meted out by corrupt brutes. Judges must decide what was reasonable for all involved to have thought in the moment as one or both parties were escalating the encounter in ways that can be hard to parse.

The judge found that there was reasonable doubt that this teen was resisting arrest. And that's noteworthy for two reasons:

1) The ubiquity of mobile-phone videos is changing the justice system. In the past, police were almost always thought credible when giving testimony about a struggle. Now, ambiguities and outright falsehoods in their narratives are exposed and judges are reacting by openly impugning the credibility of officers. As the teen's lawyer put it, "Were it not for the surveillance footage captured by the bank camera and the videos of two bystanders, the truth of what happened to Thai Gurule that September evening might never have been revealed in a courtroom." It was no longer possible to just accept the version voiced by the authorities.

2) Police unions are hugely threatened by this and their reactions highlight the staggering degrees of deference that they were accustomed to enjoying. For example, consider how Portland police union President Daryl Turner responded to the judge's ruling.

Here's an Oregonian article with his statement:

Portland police union president Daryl Turner on Monday decried a Multnomah County judge's findings last week that officers used excessive force in the arrest of a 16-year-old boy. Turner called the ruling "unfair'' and "discouraging,'' and questioned the judge's authority to second-guess the officers. He also said the judge shouldn't have relied on what he characterized as "shaky cell phone video footage.'' "What is most discouraging is that when police officers respond to a call, those officers must now be concerned that someone sitting in hindsight, from the safety of a courtroom, will not only question their actions, but their credibility,'' Turner wrote in a lengthy statement to members of the Portland Police Association.

He doesn't just complain that the case was wrongly decided. As he sees it, judges never have any business evaluating police actions or assessing the credibility of their testimony. What does he think trials are for if not to understand what happened with the benefit of hindsight? Why does he imagine that police officers are cross-examined if there is no need to determine if they are credible? His are the words of a police representative whose civic knowledge has atrophied due to years of enjoying excessive deference. Basic safeguards strike him as "discouraging."