This documentary is only 32 minutes long. It also happens to be one of this year’s Oscar nominees for Best Documentary Short Subject. The bulk of the story comes from actual footage, recorded on police-car dashboard cameras, of the 2015 arrest in Austin, TX of a schoolteacher by an Austin police officer. The officer is a white male, the teacher an African-American female, and a seemingly routine traffic stop escalates into a charge of resisting arrest. “Why?” she asks. And so does this documentary…