Elementary TV show - end of present season - SPOILER

At the end of the current season, the murder of Michael causes the FBI to look for the killer. They focus on Watson who did not commit the murder. It ended up being the police captain's daughter, Hannah. Sherlock convinces her to bring him to the murder weapon. He supposedly brings it to the FBI with Michael's blood and his fingerprints on it.

Why wasn't he arrested/convicted of the murder?

At the end of the current season, the murder of Michael causes the FBI to look for the killer. They focus on Watson who did not commit the murder. It ended up being the police captain's daughter, Hannah. Sherlock convinces her to bring him to the murder weapon. He supposedly brings it to the FBI with Michael's blood and his fingerprints on it.

Why wasn't he arrested/convicted of the murder?

Sherlock made a deal to leave the country to avoid prosecution.

Sherlock made a deal to leave the country to avoid prosecution.