The evidence I had was the specific nature of their claim. They claimed they would be showing me a video of a woman driving a car at an officer. That is a verifiable claim: if the video eventually shows something else, everyone observing it will immediately know that the initial claim was a bald-faced lie.
Contrast with a non-verifiable claim, such as “the officer felt endangered”. That isn’t something that can be definitively proven. The officer may have felt endangered. The officer may have felt perfectly safe and is simply lying to portray themselves in a better light.
Where the only “proof” of their claim is the claim itself, and they have a motivation to lie about it, we cannot trust them to speak the truth. But, where the “proof” of their claim is an objectively verifiable fact that will soon come to light, there is little reason not to trust it: they would immediately destroy their credibility to lie about a verifiable fact.
The evidence I had was their readily verifiable claim. A specific, objective fact, easily demonstrated if true, and easily refuted if false. I trusted that they weren’t so fucking stupid as to lie about an objective fact. Turns out that they were, indeed, telling the truth in that specific case. That doesn’t mean they are telling the complete, unvarnished truth about everything. They could be lying about everything I can’t verify. But I don’t need their non-verifiable claims; the verifiable ones exonerate the officers.