Selin Peers was a joined Trill, the eighth host to the Peers symbiont. He was a minister of the Trill government. He identified Dax for Ilon Tandro during her extradition hearing aboard Deep Space 9 in 2369. Selin was accepted as an expert on Trill by Tandro and testified to the nature of the joined existence.
Though he did not know Jadzia Dax, Selin testified that she retained the memories of Curzon Dax. Tandro believed this made her guilty of crimes allegedly committed by Curzon. However, Selin also testified, under questioning from Benjamin Sisko, that Jadzia Dax was a different person than Curzon Dax. (DS9 episode: "Dax")