Seantum was a Nephite member of the Gadianton band, the secret society founded by Gadianton (Helaman 8:28). He murdered his own brother Seezoram, the chief judge at Zarahemla, around 23 B.C., in an attempt to take the judgment-seat for himself (Helaman 8:27-28).
Nephi, son of Helaman, named Seantum as the murderer before the people had discovered the crime, telling them to go to the judgment-seat where they would find the judge dead and learn he had been killed by his brother, who belonged to the same secret band (Helaman 8:27-28). When Nephi was accused of conspiring in the judge’s death, he sent investigators to Seantum’s house and foretold the exact sequence: Seantum would first deny the murder, the investigators would find blood on the skirts of his cloak, and when confronted with it he would grow pale, tremble, and confess (Helaman 9:26-35). Events followed Nephi’s words: Seantum denied the crime, was found with blood on his cloak, and confessed to murdering his brother. His confession cleared the five men who had accused Nephi, and Nephi himself, who were all set at liberty (Helaman 9:36-38).