UPDATE (3rd October 10:34 BST): According to a new document uncovered by TechCrunch, expert witness and open-source software lawyer Joshua J Horowitz has disputed the FBI's account of how it located a back-end server belonging to Ross Ulbricht.

The defence of alleged Silk Road mastermind Ross Ulbricht has filed a motion asking the court to dismiss evidence and strike parts of the indictment against him.

Ulbricht's team argues that the government’s claim of how it gained access to some digital evidence raises questions and requires an evidentiary hearing, at which time it hopes to have the case dismissed. Additionally, the latest filing rejects an FBI explanation for its investigation as implausible, vague and lacking forensic evidence.

The reply memorandum of law was filed on 1st October and raises many of the same questions as the original memorandum filed on 1st August. That document asserted that the same Fourth Amendment protections could be applied in order to dismiss a significant volume of evidence collected in the seizure of Silk Road web servers.

Specifically, the defence argues that the 'fruit of the poisonous tree’ doctrine could be used to dismiss a chain of supposedly tainted evidence collected by investigators.

The defence further claims that some electronically stored information (ESI) was collected without a warrant and therefore all evidence collected using said information was inadmissible under the doctrine.

The new filing criticises the government for its failure to address a number of issues raised in the August motion.

In the document, Ulbricht’s defence counsel Joshua Dratel states:

Dratel lists a number of precedents that were not cited or addressed by the court, commenting that the court assists the government in defending unconstitutional searches by “pretending that those cases do not exist, and that it is still 1979”.

Dratel argues that opinions in Riley vs California and US vs Jones recognise that privacy interests in electronically stored information are covered by the Fourth Amendment.

“The government’s inability even to discuss those cases, and their Fourth Amendment implications, simply demonstrates the bankruptcy of its arguments in opposition,” Dratel argues.

The defence also addressed the legality of FBI’s investigation. The crux of the ‘poisonous tree’ argument is the assertion that the FBI used illegal means to identify and locate Silk Road servers in Iceland. If the defence can prove that the FBI bent the rules and located the servers using such means, all the evidence collected from them would be rendered inadmissible.

However, the FBI responded to the allegations with a 58-page filing submitted earlier this month. In the document FBI agent Christopher Tarbell offered an account of how the servers were located, dismissing allegations of illegal activities or NSA involvement.

The new defence filing criticises the government for attempting to create a "straw man" by contending that it was not necessary to explain how the servers were located in order to establish probable cause. It goes on to argue that Tarbell failed to maintain “any record of his purported means of access” to the Silk Road servers.

The filing states:

Dratel also takes issue with the timeline of the FBI’s requests to the Icelandic authorities, stating that the decision to re-image server contents in July 2013 in order to preserve evidence clearly points to a planned, orchestrated, and directed action implemented for the benefit of US law enforcement.