From the review:
The cops in 1864 don’t play by 21st century rules. There are no such things as Miranda Rights or making sure suspects aren’t roughed up.
In fact, suspects are just killed outright, at times.
What I like about the series is that the writers, including Fontana and Rokos, have used 19th century melodrama as a base template, but then added complex characterizations and moral views, and dimensions to the themes of good versus evil.