Canada

Quebec police are refusing to answer questions from the oversight body investigating civilian deaths and serious injuries during police interventions. This is after

[Police] unions also challenged the obligation for officers to meet with ... investigators. They argued that those rules infringed on their members’ constitutional rights to stay silent and not incriminate themselves.

It's part of a national trend:

in British Columbia, police officers rarely co-operate with the Independent Investigations Office ..., while they often only partly co-operate with independent oversight bodies in other provinces.