As a society we generally do not condone or accept vigilantes. The emphasis in modern society is that people will instead resort to the law. On the criminal side there are the police and other law enforcement agencies with a duty to address the criminal wrongs perpetrated against a person, group, company, etc. On the civil side persons must enforce for themselves by way of civil actions. These civil lawsuits can be in regards to almost anything. Examples include such things as odors emanating from the neighboring facility, dissatisfaction with an equipment purchase you made or with the services provided by a safety consultant you retained, or a workplace injury.
The litigation process is filled with rules and processes. A mistake in some of these rules/processes can result in the loss of a case. One of the most basic (and longest) processes of civil litigation, and also perhaps the most important, is that of discovery. One of the methods of discovery is that of an oral deposition.