Perhaps the most distinguishing feature of a grand jury is its secrecy. Grand jury proceedings are not public and grand jurors are required to take an oath about secrecy. Another distinguishing feature is that traditional rules of evidence do not apply in the grand jury setting. Prosecutors are able to present evidence that might be excluded at trial for being hearsay. Grand juries also have the power to compel witnesses to testify.

The grand jury usually is composed of more citizens than the petit jury. In Texas, however, grand jurors are composed of 12 jurors. Second, the grand jury only hears from the prosecutor, not the defense. The prosecutor decides what witnesses to call and which individuals receive immunity for their grand jury testimony. The subject or target of a grand jury is not allowed to bring an attorney and present evidence. The grand jury has broad powers to subpoena witnesses, including the defendant. The defendant can assert his Fifth Amendment right against self-incrimination at the grand jury proceeding.