Application to take a deposition is usually made by motion; statutory provisions, or the nature of the proceeding, may require it to be done by petition or bill in chancery.

By statute, in most jurisdictions, after due notice to all parties litigant, upon proper motion or petition, there issues out of the court to which application is made, as a matter of right, under its seal, a commission to take testimony, or dedimus potestatum, as it is called. This commission is usually directed to a certain specified person, as commissioner, or to any judge, master in chancery, notary public, or justice of the peace, of the county in which the deposition is to be taken, commanding him to take the deposition of X, a material witness in the said cause, upon interrogatories, oral or written, as the case may be, to be propounded by either party, at a specified time and place.

The commissioner must not be of counsel for either party, nor in any way interested in the result of the action, nor in any manner in favor of or prejudiced against either litigant.

In the absence of statute or rule of court requiring it, the notice need not name the commissioner before whom the depositions are to be taken, but must state the names of witnesses, and time and place with certainty.