Maybe that's how things work with legal procedure elsewhere but it's not the case here.
Of course it is. Even if not a legal burden they have subliminally shifted the burden of proof by what they have asserted to the jury to be true.
Once any defense puts forth to the jury someone specifically (by name) is the real killer, you can bet the bank, the jury is going to want to have irrefutable proof as to what they have asserted is factually true.
After all what they are really asking this jury to do is to set aside all of the compelling evidence entered thus far pointing to CM only, and now believe DK is SODDI instead.
They are the ones who declared this to be true in OS. Now the jury will expect them to man up proving what they have asserted.
Imo, they would have been much better off if they had made the SODDI suspect more generic by not naming anyone else specifically by name. Proclaiming they really dont know who did it, but know it wasnt the one accused on trial.
The DT in the Daron Wint quadruple murder case mistakenly did the very same thing specifically naming his two brothers as the (cough cough) real killers.
They crashed, and burned, because in the end, they were unable to produce any evidence to the jury this was remotely true, even though the DT had asserted it would be shown during the trial when they did their own OS.
IMO. It's never wise to over promise anything to any jury, and then not produce what they have promised.
Jmo