Jimmy Hoffa Agreement. He played a major role in the growth and development of the union, which eventually became the largest (by membership) in the United States with over 2.3 million members at its peak, during his terms as its leader. Hoffa became involved with organized crime from the early years of his Teamsters work, and this connection continued until his disappearance in 1975. He was convicted of jury tampering, attempted bribery and fraud in 1964, in two separate trials. He was imprisoned in 1967 and sentenced to 13 years. In mid-1971, he resigned as president of the union as part of
Jimmy Hoffa 1975. Police and Hoffa's family had long believed O'Brien played a role in Hoffa's disappearance. O'Brien, however, had previously denied ever being involved in Hoffa's disappearance or that Hoffa had ever been a passenger in his car. In a first-season episode of the Discovery Channel show "MythBusters", titled "The Hunt for Hoffa", the locations in Giants Stadium where Hoffa was rumored to be buried were scanned with a ground penetrating radar to see if any disturbances were present that would indicate a human body had been buried there. They found no trace of any human remains. No human remains were