At 1931 Menshevik Trial, Rubin refused to confirm the existence of a Menshevik organisation. Although he agreed to make false statements regarding Riazanov's correspondence with other secret Mensheviks, he claimed that this was done on the basis of "great personal trust" rather than organisational discipline. As a result of this failure to fully cooperate with his prosecutors, Rubin was sentenced to five years in prison. Although he attempted to shield Riazanov from the worst charges, Rubin emerged from the experience "morally broken, destroyed, degraded to a state of complete hopelessness".