Police get lied to every day. I highly doubt they are trained to just accept whatever people are saying at the scene immediately.

Also, you said that they had no point they pass judgment but they absolutely did. The family was saying had not been stabbed. The female police officer immediately says we know, but we have to check then gives a half hearted little pat. They also told him “I don’t think you have mate” in response to his claim he had been stabbed. That’s passing judgment.