” ... odd is that the DA would take the case to a Grand Jury if he did not consider the evidence adequate to go to trial in the first place.”
That caught my attention, too. It could be that it was brought to the GJ by a prior DA? My memory is that there were a couple of DAs over the course of this story that went on for years.
Typically a Grand Jury is impaneled for only a specific period. Generally 90 days.
The GJ will then meet only once a week and then only if the Prosecutor has a case for them to review.
Only on rare occasions is a special GJ empanelled for a specific case that will be seated long term.
Judges are reluctant to seat a special GD because it is a great imposition on people’s time and it is difficult for people to remain impartial on such cases today because of all of the news coverage of such a case.
A prosecutor could certainly take the same case to a GJ more than once. If more than one prosecutor worked the case it certainly could have gone before different GJs.