In the argument with the mayor/police chief Baptiste referred to Ian Garrett (who was v wealthy) having sponsored the chief's career. And Garrett had other "friends" in the police, eg the one who let him in the cell the night tony was arrested.
Perhaps Garrett also knew mark somehow?
The journalist who tapped the phones thought Garrett was the murderer, because of the message from Emily he hacked but also perhaps because of the evidence zianne found.
We only have mark's word for it being the sobriety coin.
Mark also has sticky-out ears, like the drawing.