> These charges were dismissed partly because he had already been sentenced to life in New York

It was further complicated because a couple of the law enforcement officers involved with setting up one of the six murder-for-hire scams* stole the Bitcoin Ulbricht paid and it was also felt that trying to prosecute based solely on the other chat logs would have been difficult. The FBI agent who arrested Ulbricht was interviewed about it recently[1].

* The other five are said to not have been law enforcement, which makes it curious the number of times Ulbricht was scammed in this manner.

[1] https://risky.biz/RB770/