An Insignificant Case by Phillip Margolin

Charlie Webb is not exactly what you'd call a successful lawyer. He's barely hanging on when a judge assigns him a case. He's to represent an eccentric artist who calls himself Guido (born Larry). Guido has stolen back a painting he sold to a restaurant because the owner didn't display it as prominently as he would have liked. While he was stealing it back, he also stole a thumbdrive he found in her safe. And when he looked at the contents of the thumbdrive he realize what a ticking time bomb it was. The thumbdrive showed the rape and murder of a young woman along with several other rapes. It turns out that the restaurant owner was part of a sex trafficking ring. Since several influential men are seen on the video, everyone and his brother is trying to get their hands on it. And soon bodies are falling. It was a very compelling story and you really want Charlie to succeed on his first big case.