A death qualified jury is considered a prosecutors' jury. The DA knew that they could not reduce the charges just before selecting a jury, because that would send a clear signal to potential jurors that they did not have the evidence to support the charges (murder one) -- hardly the best way to begin voir dire. That's why they stopped the death penalty nonsense now.
The problem is that even if the State wants to go to murder two, they still have to prove malice aforethought. I can't see how the evidence that we know of can possibly support that finding either. Moreover, I would love to hear the evidence that supports murder (unlawful killing) versus an accident.
As regards the Laci Peterson case, my position has always been that I do not know if Scott murdered Laci or not. However, no one, anywhere, has ever cited clear and unyielding proof of: intent, planning, deliberation and malice aforethought. Moreover, unlike Casey's case, prosecutors had the bodies in Scott's case. I expect Scott to receive a second trial.