Villegas was co-owner and vice-president of Plaza Health Laboratories, a blood testing laboratory in Brooklyn, New York. On two occasions between April and September, Villegas loaded containers of numerous vials of human blood generated from his business into his personal car and drove to his residence in a condominium complex in Edgewater, New Jersey. There he removed the containers from his car and carried them to the edge of the Hudson River, where he placed them in a bulkhead that separates his condominium complex from the river. The vials were placed during low tide in a crevice in the bulkhead that was below the high-water line. In May, a group of eighth graders on a field trip on Staten Island discovered numerous glass vials containing human blood along the shore and in the water. Ultimately 70 vials were recovered; some of them were cracked and others remained intact. The vials, some of which contained blood infected with hepatitis-B virus, were traced back to Plaza Health Laboratories. In September, a maintenance worker at the condominium complex discovered other vials wedged in the bulkhead; they were also traced back to Plaza Health Laboratories. The United States brought a criminal action against Villegas, charging him with "knowingly discharging pollutants from a point source into a water of the United States." The Clean Water Act defines "point source" to be a "discernable, confined and discrete conveyance, including but not limited to any pipe, ditch, tunnel, conduit, well, discrete fissure . . . ." but does not enumerate human beings among the enumerated items. After Villegas was convicted by a jury, he appealed, contending that the government had not established one necessary element of the crime with which he was charged, namely that the discharge had come from a "point source" as that term is used in the statute. Should his conviction be reversed on the grounds there was no discharge from a point source?