Ross Ullbricht did not get a fair trial. Evidence was withheld to protect the agents, who also stole Bitcoins.
The murder charges was never used in court, they only fabricated that story, to make him look bad, and the sentence is clear evidence of that.
I doubt they were fabricated but it may have been entrapment. If you're going to say evidence was fabricated then you might as well say the entire evidence they had against him was fabricated too.