How do I write the thought processes of a morally bad person, who's also a coward?

So recently I got the idea to do a character study on this one character who is, arguably a bad person in canon. (He's related to a rapist and was kind of shifting between believing and not believing him, and sided with him when he was wrongfully let free, even though he's heard contradictory evidence)

But i've written roughly a few hundred words and I just can't seem to properly get into his head space. Any tips would be welcome.