Prosecutors are given broad freedom to conduct their investigations through-out the grand jury process; their power is not without legal and ethical limits, however. For example, courts have discretion to quash subpoenas that have been issued without a proper purpose.Unlike law enforcement officials who may use deceptive tactics throughout an investigation, prosecutors are subject to professional rules of responsibility. All lawyers are subject to some variation of Rule 4.2 of the Model Rules of Professional Responsibility—the No-Contact Rule—which prohibits a lawyer from communicating with a represented individual. Prosecutors, however, have escaped the Rule’s reach by communicating with represented individuals through the use of undercover informants.
Robbins, Ira, "Sham Subpoenas and Prosecutorial Ethics" (2021). Articles in Law Reviews & Other Academic Journals. 1937.