More specifically, it means the prosecution doesn’t have a case. The question before a grand jury is whether there’s enough evidence to take it to trial. They take the prosecution’s claims at face value, and ask if that would be enough for a conviction, assuming there was no dispute over the facts.

There’s no defense present, because that’s not the question. The grand jury does not weigh evidence or anything; that’s for the petit jury. Decisions about admissibility of evidence is for the trial judge.

Grand juries typically indict 95%+ of the cases presented. You need to have a really, really bad case to lose at the grand jury stage.

We need to hurry up and pass the 61st amendment! (/s)