In 1934 some self proclaimed 'expert' on crime and hoodlums, testified before Congress that machine guns, Thompsons etc., were favored by criminals, and then also, that the 'silencers' could be used by the criminal organizations to carry out gangland 'hits'. As a result of this ill advised testimony, Congress passed the law with a tax stamp required to own either, with the amount of the tax so high that no one but gangsters could afford to pay it.