I'm basing my information on two minutes of ESPN, so it's probably not completely accurate.
The defendant is entitled to a court hearing to determine if there is probable cause for a trial. The Prosecution said they weren't ready for the hearing yet, so they got a continuance to do it another day.
It might be possible to have a Grand Jury determine probable cause instead of a Judge at a court hearing, in which case, they'll do that (or they might have to do both). They haven't gone to a Grand Jury yet either. I don't want to speak for Massachusetts law to say it can be done that way.
ETA: More or less what Timby said.