@ Mikey The have not confessed to murder, or changed their plea to guilty. If they had, that would have brought the trial to a halt.
Instead, they admit to killing, but not murder, and their defence is that it was an act of war, so the trial goes on ,the evidence is heard, the various statements are made, the judge summarises, and the jury consider their verdict.
Of course it was murder- a vile, brutal and heinous act. But they are entitled under our legal system to make a case.