How do grand juries and petit juries differ?

A normal (petit) jury hears evidence of a case after the arrest and arraignment of the accused. A grand jury hears evidence before the case is filed and may issue indictments based on the evidence...

A normal (petit) jury hears evidence of a case after the arrest and arraignment of the accused. A grand jury hears evidence before the case is filed and may issue indictments based on the evidence...

Grand Jury hear evidence to determine guilty or innocence of a defendant.

Correct.

A trial jury