No they are not allowed to both, they must choose between the two.
Yes. Grand Jury.
Depending on the state you are in (some use the Grand Jury System and others use the Preliminary Hearing system) it is the hearing at which the defendant is formally charged with the offense he was arrested for.
A 'preliminary hearing.' aka. a probable cause hearing.
A preliminary hearing, in the context of criminal law, is used to determine whether probable cause exists to believe that the offense charged in the information has been committed by the defendant. The hearing officer considers the evidence and reaches a decision on the issue of probable cause. In those states which do not employ the Grand Jury System for indictments, the Preliminary Hearing serves the same function.
It is an indictment issued by a Grand Jury after the defendant has already had an initial appearance in his case, and the case has been set for a preliminary hearing before court. However, in the meantime the State has indicted the defendant by grand jury proceedings. This 'supervening' action by the Grand Jury indicts the defendant and has the effect of rendering all previous court actions in the defendant's case null and void.
A preliminary hearing might better balance the rights of society and the rights of the accused. With a preliminary hearing a judge is going to weigh the evidence and decide if there is enough evidence for trial. With a grand jury, a group of citizens decides if there is enough evidence for trial.
Although grand juries and trial juries are both made up of average people who were called for jury duty, they serve entirely different purposes. A grand jury helps determine whether charges should be brought against a suspect, while a trial jury renders a verdict at the criminal trial itself. Put differently, a grand jury hands down an indictment at the beginning of a case, while a trial jury decides guilt or innocence at the very end (not counting the appeal process).
A Grand Jury only hears witnesses brought forth by the prosecutor. The defense attorney(s) and defendant(s) are not present at the hearing. Witnesses are not allowed to have their attorney present, but may excuse themselves to confer with legal counsel outside of the hearing/court room.
In Nevada law: Marcum notice is a notice given to defendant's counsel that the District Attorney will take his case to a Grand Jury; I believe it is used when a preliminary hearing has not produced a favorable outcome for the prosecution and they decide to pursue the case, the provide more information to the Grand Jury in an effort to obtain an indictment.
An information is where the district attorney or prosecutor charges a defendant of some crime or crimes, whereas an indictment is where the a defendant is charged after a grand jury has heard the evidence. The evidence usually meets a certain standard such as legally sufficient standard or probable cause.
•Initial Appearance •Filing Charges •Preliminary Hearing •Grand Jury •Arraignment •Trial •Sentencing
There is nothing necessarily proper or improper about it. The prosecutor at least in CA has an absolute right to have either a preliminary hearing or a get a grand jury indictment.