In order to get a subpoena, wouldn't the prosecutor have to show probable cause that a crime was committed?

According to news outlets (example), Mueller has subpoenaed a Trump organization.

I did some research and the answer seemed to be 'yes', but I was talking it over with a friend of the family who took some law classes and the answer was 'not necessarily'.

So is probable cause that a crime was committed necessary for a subpoena to be issued?

2 Answers 2


A grand jury subpoena needs to not be oppressive or unreasonable: see US v. R Enterprises, 498 US 292. The purpose of a grand jury is to determine if there is probably cause: "the Government cannot be required to justify the issuance of a grand jury subpoena by presenting evidence sufficient to establish probable cause, because the very purpose of requesting the information is to ascertain whether probable cause exists". The court held that

The unique role of a grand jury makes its subpoenas much different from subpoenas issued in the context of a criminal trial. Thus, this Court has held that a grand jury may compel the production of evidence or the testimony of witnesses as it considers appropriate, and that its operation generally is unrestrained by the technical procedural and evidentiary rules governing the conduct of criminal trials

Also note that

The grand jury's investigatory powers are nevertheless subject to the limit imposed by Rule 17(c), which provides that "the court on motion made promptly may quash or modify the subpoena if compliance would be unreasonable or oppressive" (emphasis added). Since a grand jury subpoena issued through normal channels is presumed to be reasonable, the burden of showing unreasonableness, as the above language indicates, must be on the recipient who seeks to avoid compliance

So the bar is lower for a grand jury investigation, such as this one.

  • 2
    As is often said, a prosecutor can indite a ham sandwich in Grand Jury.
    – hszmv
    Commented Mar 15, 2018 at 19:38

user6726's answer correctly notes that probable cause is not required to issue a grand jury subpoena. However, this is not because the bar is lower for a grand jury. It is because probable cause is the standard required by the Fourth Amendment to issue a warrant, and the Fourth Amendment does not apply to subpoenas.

The nature of a subpoena

Rather than a warrant to arrest or search the property of a suspect, a subpoena is an order to a witness to produce documents or provide testimony. Subpoenas are available in civil as well as criminal proceedings, and can be obtained by any party. Normally a party who requires the disclosure of documents under subpoena before trial must show that (1) the documents are evidentiary and relevant, (2) they cannot otherwise be procured with due diligence, (3) they are needed for trial preparation, and (4) the application is made in good faith and is not a 'fishing expedition': United States v. Nixon, 418 U.S. 683 (1974), pp 699–700. As pointed out by user6726, a lower standard applies before a grand jury.

In criminal investigations, most subpoenas are aimed at third-party recordholders: Slobogin, 'Subpoenas and Privacy' 54 DePaul Law Review 805 (2005), p 809. A third-party subpoena eliminates the possibility the suspect will destroy the evidence and normally eliminates the target's ability even to challenge the government's action: Slobogin, p 811. A typical example is a subpoena directed to a bank to produce a suspect's financial records. We don't have the facts yet, but in this case, it seems likely that a subpoena has been issued to the Trump Organization in its capacity as a third-party recordholder.

Subpoenas to witnesses who are also suspects

I originally stated that a subpoena is directed at a witness rather than a suspect. As pointed out in the comments below, a suspect can be a witness as well. But at common law, a subpoena could not be issued to a defendant in a criminal case because of the privilege against self-incrimination: R v Purnell (1748) 1 Wils 239, p 243. In Boyd v. United States, 116 U.S. 616 (1886), pp 634–635, the Supreme Court held that the Fourth Amendment protection from unreasonable searches and seizures and Fifth Amendment privilege against self-incrimination reflected this part of the common law.

In a line of cases summarised in Slobogin, pp 814–821, the Supreme Court departed from Boyd and limited the scope of the Fourth and Fifth Amendments. Significantly, in Hale v. Henkel, 201 U.S. 43 (1906), p 73, the Court held that the Fourth Amendment does not apply to subpoenas, and the Fifth Amendment does not apply if the witness is immune from prosecution. Later, in Fisher v. United States, 425 U.S. 391 (1975), p 408–410, the Court held that the Fifth Amendment does not apply to a subpoena to produce self-incriminating documents unless the act of production has a testimonial aspect.

In this answer, I originally stated that the Fifth Amendment would generally make it pointless to issue a subpoena to a suspect. That took the point too far, but United States v. Hubbell, 530 U.S. 27 (2000) demonstrates that the Fifth Amendment still imposes significant constraints on the use of subpoenas against suspects by requiring prosecutors to grant immunity to witnesses in many cases. A more accurate summary appears in Cole, 'The Fifth Amendment and Compelled Production of Personal Documents After United States v. Hubbell – New Protection for Private Papers?' (2002) 29(2) American Journal of Criminal Law 123:

[T]he net result of the Court's decision in Hubbell is to limit the practical ability of prosecutors both to compel production of documents and to use the contents of those documents in prosecuting the witness who produced them. As a result, prosecutors conducting criminal investigations may be more likely to use search warrants, rather than subpoenas, to obtain documents from individuals.

  • This isn't true. Suspects receive subpoenas for testimony and documents, too.
    – A.fm.
    Commented Mar 16, 2018 at 3:06
  • @A.fm Indeed, but witnesses are entitled to the privilege against self-incrimination (which is why I said it would generally be pointless, rather than impossible, to subpoena a suspect). Are you saying it is common to subpoena suspects to give evidence against themselves?
    – sjy
    Commented Mar 16, 2018 at 3:14
  • What are you asking? You said subpoenas are directed at witnesses, not suspects. I said suspects receive them, too. Then you say, "Indeed"? Nonetheless, subpoenas are simply legal documents requesting testimony or documents; anyone can receive one.
    – A.fm.
    Commented Mar 16, 2018 at 3:23
  • Sorry to comment twice, but your statement, "Indeed, but witnesses are entitled to the privilege against self-incrimination (which is why I said it would generally be pointless, rather than impossible, to subpoena a suspect)" makes me wonder if you simply made a typo on either witness or suspect. Why would witnesses having 5th Amendment protection have anything to do with whether or not it's pointless to subpoena a suspect? Whether a witness has that protection has no bearing on the rights of another party.
    – A.fm.
    Commented Mar 16, 2018 at 3:24
  • @A.fm.: If a crime is committed by two (or more) individuals, Bob and Alice, and Alice agrees to testify against Bob for a lesser charge or sentence, Alice would be a suspect and subpoenaed at the same time.
    – hszmv
    Commented Mar 16, 2018 at 14:43

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