If the FBI systematically performed traffic confirmation on the Tor network, this would be a rather sloppy sources and methods cover, as they would eventually be forced to disclose the existence of the traffic confirmation system.
If the servers' IPs were obtained as a result of a passive traffic confirmation system that breaks Tor's anonymity, I would expect a detailed parallel construction to demonstrate an alternate explanation for how they unmasked the servers.
Any defense attorney worth his salt is going to request the evidence relating to the method of de-anonymization of the Silk Road servers. If a traffic confirmation system was used, the prosecution would be forced to disclose that to the defense, which could very well raise a solid argument that it violated the defendant's Fourth Amendment rights.
My guess is that the FBI used the gmail account information and early public silk road advertisements to obtain a warrant from a friendly judge to remotely monitor DPR's computer, and waited until he connected to the server. It's also possible that they exploited the web server, as was the case with FreedomHost.
If the servers' IPs were obtained as a result of a passive traffic confirmation system that breaks Tor's anonymity, I would expect a detailed parallel construction to demonstrate an alternate explanation for how they unmasked the servers.
Any defense attorney worth his salt is going to request the evidence relating to the method of de-anonymization of the Silk Road servers. If a traffic confirmation system was used, the prosecution would be forced to disclose that to the defense, which could very well raise a solid argument that it violated the defendant's Fourth Amendment rights.
My guess is that the FBI used the gmail account information and early public silk road advertisements to obtain a warrant from a friendly judge to remotely monitor DPR's computer, and waited until he connected to the server. It's also possible that they exploited the web server, as was the case with FreedomHost.