HUAC's investigation of atomic espionage allegations at Berkeley Radiation Laboratory

The House Un-American Activities Committee’s investigation of atomic espionage allegations at Berkeley Radiation Laboratory in 1949 widened scrutiny from a suspected spy to a circle of physicists linked by study, politics, and surveillance. Four former students of J. Robert Oppenheimer were subpoenaed, and Oppenheimer himself was called to testify. The inquiry turned on a difficult distinction: what investigators suspected they knew from surveillance, what witnesses would say in public, and what could be established through admissible evidence.

Background and Targets

In the spring of 1949, the House Un-American Activities Committee, commonly known as HUAC, launched a major investigation of alleged atomic spying at Berkeley Radiation Laboratory. The four former students subpoenaed were David Bohm, Rossi Lomanitz, Max Friedman, and Joseph Weinberg. The inquiry’s interest in Weinberg rested in part on a 1943 wiretap that had captured him talking with Steve Nelson about the atomic bomb.

The Committee’s lawyers understood that the wiretap had been conducted without a warrant and would not stand up in court. That created a procedural bind: they believed the intercepted conversation implicated Weinberg, but could not straightforwardly use it to prove the allegation. On April 26, HUAC brought Weinberg face-to-face with Nelson. Weinberg denied that he had ever met him. The lawyers believed Weinberg had perjured himself, yet proving that claim without relying on the wiretap appeared difficult. They therefore looked to testimony from Bohm, Friedman, and Lomanitz to strengthen their case.

The Students and the Pressure to Testify

Bohm was uncertain whether to testify and, if he did, whether he should discuss his friends. Albert Einstein urged him to refuse, even if refusal meant going to jail. Bohm did not want to invoke the Fifth Amendment: because membership in the Communist Party was not illegal, he reasoned, it gave him nothing to incriminate himself about. His initial inclination was to discuss his own political activity while declining to testify about others.

Knowing that Lomanitz had also been subpoenaed, Bohm contacted him in Nashville, where he was teaching. Lomanitz had struggled to find lasting employment after the war; whenever he secured a decent job, the FBI would tell his employer that he was a communist, and he would lose the position. Despite this precarious situation, he traveled to Princeton to see Bohm. The investigation thus reached beyond the hearing room: government scrutiny had already helped shape the professional circumstances of one of the witnesses it sought to question.

Oppenheimer’s Encounter and Testimony

Soon after Lomanitz arrived, he and Bohm were walking along Nassau Street when Oppenheimer emerged from a barbershop. Oppenheimer had not seen Lomanitz for years, though the two had kept in touch. In a 1945 letter, Oppenheimer had urged him to hold on through a difficult period and invited him to visit when he was able. Now Bohm and Lomanitz explained the subpoenas and their uncertainty about what to do. According to Lomanitz, Oppenheimer became agitated and exclaimed, “Oh, my God, all is lost. There is an FBI man on the Un-American Activities Committee.” Lomanitz thought the reaction “paranoiac.”

Oppenheimer had reason to be alarmed: he, too, had received a subpoena. He knew that Illinois congressman Harold Velde, a Committee member, had formerly worked for the FBI and had investigated Berkeley Radiation Laboratory during the war. Oppenheimer later described his encounter with the former students as a brief, two-minute conversation in which he advised them to tell the truth; he recalled them answering that they would not lie. Lomanitz’s account of Oppenheimer’s alarm presents a sharper, more anxious version of the meeting, leaving the encounter’s tone at odds with Oppenheimer’s later compressed description.

On June 7, Oppenheimer appeared before six congressmen in a closed executive session. He ostensibly attended as chairman of the General Advisory Committee of the Atomic Energy Commission, but the questioning focused on alleged atomic spies rather than nuclear weapons policy. Apprehensive, he chose not to bring a personal lawyer. Instead, he brought Joseph Volpe and introduced him as the Atomic Energy Commission’s general counsel. The first question asked whether Oppenheimer knew that a Communist cell existed among scientists at the Radiation Laboratory. He denied knowing of one. Asked about his former students’ politics, he said he had not known before the war that Weinberg was a communist and described Weinberg’s postwar expressed views as not following the communist line. Over the two-hour session, Oppenheimer was cooperative and forthcoming.

Testimony and the Limits of the Inquiry

Bohm testified before HUAC in May and again in June. On the advice of Clifford Durr, a civil-liberties lawyer, he refused to cooperate, invoking the First and Fifth Amendments. Princeton University issued a statement supporting him for the time being. His position reflected the distinction that had troubled him from the outset: he could regard his own political activity as no basis for criminal exposure while still resisting demands to testify about other people.

The investigation’s evidentiary problem remained visible throughout this sequence. The Committee’s lawyers believed Weinberg had lied, but the wiretap that informed their suspicion was not usable in court; they sought other witnesses while those witnesses faced the risk of exposing friends and political associations. Oppenheimer’s own appearance extended the inquiry’s reach to a senior scientific adviser, but his testimony did not erase the tension between suspicion, surveillance, and proof. In the account of the proceedings, the investigation is defined less by a conclusive public finding than by the pressure it placed on witnesses and the uncertainty surrounding what the available evidence could establish.