Nephi’s new prophecy is to deliver the murderer. Seezoram was murdered by his brother, and Nephi tells the people to go to that man, and declare that Nephi has indicated that he is the murderer. Nephi correctly predicts that the brother will deny his guilt.
Cultural: Mormon is interested in this story because of prophecy, not because of the intricacies of Gadianton politics. However, we may be more curious, and wonder why the brother would slay his own brother. Politics in Mesoamerica were intimately linked with kinship groups. The succession in rulership frequently went from brother to brother rather than from father to son. When Seezoram’s brother kills him, it is most probable that the murdering brother would be next in line for the chief judge seat, and therefore had a very powerful political and economic incentive to murder.
To understand this more fully we must remember that in the Mesoamerican economy, access to wealth was controlled politically, and secondly that the judgeship among the Nephites did not function by election, but rather following kin rules. The role of the “voice of the people” appears to have been able to function as a “vote of confidence/no confidence” to allow the ruler to remain, or to oust him. As we saw earlier, this very Nephi was likely removed from the judgment seat by that “voice of the people.”