In 1926 two former agents of the Bureau of Investigation, Frederick Weyand and Lawrence Leatherman, gave affidavits to William G. Thompson describing the role of the Bureau of Investigation (the ancestor of the FBI) in the Sacco-Vanzetti case. The affidavits seemed to confirm long-held beliefs among the Sacco-Vanzetti Defense Committee that the case had been a political frame-up from start to finish.
"Some time before the arrest of Sacco and Vanzetti on May 5, 1920," Weyand deposed, "—just how long before I do not remember—the names of both of them had got on the files of the Department of Justice as Radicals to be watched.... Both these men were listed in the files as followers or associates of an educated Italian editor named Galleani." Federal authorities, he continued, had not been involved in the arrest of Sacco and Vanzetti, but the Boston office had immediately begun closely watching the activities of the defense committee with the help of undercover agents, and Weyand and other agents had attended the Dedham murder trial for the purpose of gathering information about radical activities. A bureau spy, Carbone, had been placed in Dedham jail for the purpose of obtaining information from Sacco about either the Wall Street bombing of 16 September 1920 or the South Braintree murder but without result. "The understanding in this case between the agents of the Department of Justice in Boston and the District Attorney followed the usual custom," he continued, "that the Department of Justice would help the District Attorney to secure a conviction, and that he in turn would help the agents of the Department of Justice to secure information that they might desire." In particular, the department hoped to secure proof of Sacco and Vanzetti's anarchist beliefs as a basis for deporting them should they not be convicted of murder. Agent William West had exchanged information with Katzmann, including information on the defendants' radical activities to be used in their cross-examination. Weyand concluded that neither he nor any other agents of the Boston office involved in the case believed that Sacco and Vanzetti had had anything to do with the South Braintree crime, which in their opinion had been committed by "a gang of professional highwaymen."
Leatherman's affidavit noted that he had not joined the Boston office of the bureau until September 1921 but confirmed virtually everything