I'll bet Mark won't be staying in that hospital once the arrest warrant is issued.
A lot will depend on his diagnosis. If he's diagnosed as nuts, he will still be arrested but may be held in a secure psyc facility under police watch or held in solitary confinement with suicide precautions at the county lock-up. My guess is that the DA doesn't want him charged/arrested before they know what these psychiatrists are likely to be testifying to later. That impacts on planning of the investigation, timing of arrest and trial strategy.