Flowers had been smoking crack in his apartment over a 24-hour period when a strange man came to his door. After arguing with Cross, Flowers told police fired three time when he saw the man reach for a weapon.
Prosecutor Steve Gibbon on Thursday told jurors that Cross' weapon, which turned out to be a BB gun, was found securely in his waistband.
"If he'd had it out, it would have been on the floor," the prosecutor said.
"What really happened is the defendant filled in the blanks" in his story, Gibbon said. "He had seen some things to make him suspicious and he extrapolated to, 'They must be here to kill me.' ... When we're talking about taking a life, that's not good enough."
But defense attorney Jason Poppleton said Flowers was justified in the killing.
"Ken shot Cisco Cross because Cisco Cross brought a gun to Ken's apartment," the defense attorney said. "Ken shot Cisco Cross because he was going for that gun. When that happens, you don't wait for bullets to fly."
Before Cross was shot, Flowers had twice been deported from the United States to Belize, where he is believed to have been a prominent street gang member.
Belizean media reported in April 2010 that Flowers had been shot and killed in Utah. Flowers had indeed been shot in the head, shoulder and hand during a fight in Murray but survived.