I don’t think Dean has it in him to kill someone, but then again it would be a good plot twist and make sense with his fair hatred of his family (whom Walsh allegedly associated with) to have him crack and play a part in it
I also wonder whether Liz’s mum saying Liz had “balls of steel” at the start of the season was a red herring. Whatever Liz’s mum had on Liz, she told Eugenia (the carer/cleaner), and I don’t think Eugenia would tell Liz she was a good person if she knew Liz participated in someone’s murder/hiding it.
IMO, Liz’s mum knows that Liz helped downplay Fiona’s responsibility in the driving accident that killed the kid and told Eugenia this.
Liz seems like she has good intentions but maybe is prone to getting wrapped up in toxic relationships because of how her mum’s abuse affected her mentally, and is easily pressured to do things. Of course, being easily pressured doesn’t excuse her from wrongdoing
Fiona’s story doesn’t line up with the other witnesses’ IIRC - she said that she and Liz stayed in the car for hours after Dean left to chase Ram and the other guy, who she said went after Walsh first. But the witness said that he saw a woman and an Asian man (supposedly Ram) chase Walsh down. So starting to suspect Fiona for sure, especially given she probably doesn’t know anyone saw the chase and so saw an opportunity to lie. I do feel sorry for Fiona, and for all of them tbh