The men were convicted in the 2011 shooting deaths of four Americans aboard their yacht off the coast of Africa.
The yacht's owners, Jean and Scott Adam of Marina del Rey, Calif., and their friends, Bob Riggle and Phyllis Macay of Seattle, were killed several days after they were taken hostage at sea.
The pirates originally wanted to bring the Americans to Somalia to ransom for millions of dollars.
The Somalis have been found guilty of 22 crimes that are eligible for the death penalty.
The jury began deciding whether to give the men the death penalty or life in prison on Thursday. Deliberations will continue Friday.