In 1947, a group of nineteen notable Hollywood writers, directors, and producers, including Trumbo, were summoned to appear before the House Un-American Activities Committee chaired by Rep. John Parnell Thomas. Trumbo was one of the ten witnesses in this group who refused to state whether they "were now or had ever been members of the Communist Party." They became known as the Hollywood Ten. The collection includes hate mail Trumbo received during the HUAC hearings, many of them containing anti-Semitic remarks and threats of physical violence.
The Ten invoked the First Amendment in refusing to answer government inquiries into their private beliefs and political associations. Trumbo responded to the committee’s stated concerns of the possibility of Communist propaganda infiltrating Hollywood films by submitting into evidence screenplays he had written, but the committee did not accept them or attempt to find any Soviet influence in his work. He was cited for contempt of Congress for refusing to testify.
In documents in the collection, Trumbo states that the Ten refused to testify not because of expediency, embarrassment, or in order to follow a party line, but because they saw it as their right to their own political ideologies and associations. While he was relatively open about his political stances, Trumbo believed that stating his affiliations to Congress would be giving in to undue state intervention into his life. Documents from the collection suggest that Trumbo felt the strategy of resting their defense entirely on the First Amendment and not invoking the Fifth Amendment right to avoid self-incrimination showed that the Ten’s legal team was more interested in absolute victory for abstract principles than the best interests of their clients. After numerous attempts at appeal the Hollywood Ten were fined and imprisoned. Trumbo served nine months between 1950 and 1951 in the Federal Correctional Institution in Ashland, Kentucky. The collection includes numerous letters written from prison to his wife and children.