A Grand Jury in Colorado consists of 12 to 23 citizens who are summoned to investigate suspected criminal activity, while a Petit Jury, composed of 6 to 12 individuals, is responsible for determining a defendant’s guilt or innocence.
The grand jury process is most common in
- federal cases and
- high-profile state cases.
Grand juries are not necessary to charge suspects – the prosecutors can bring charges at their own discretion. But having a jury of the suspect’s peers listen to the evidence and make the charging decision lends the case credibility in the eyes of the public.
Below, our Denver Colorado criminal defense lawyers discuss the following frequently asked questions:
- 1. What is a grand jury in Colorado?
- 2. How big are grand juries?
- 3. How are they different from trial juries?
- 4. What happens during grand jury proceedings?
- 5. Do witnesses need to appear if they are subpoenaed?
- 6. Are the indictments sealed?
- 7. How long does grand jury duty last in Colorado?
- 8. Is the federal process different?
- 9. What if I get subpoenaed to appear before a grand jury?
- 10. Do I have the right to remain silent?
- 11. Can I get immunity?
- 12. Can I challenge the grand jury indictment?
1. What is a grand jury in Colorado?
A grand jury is a group of local citizens who decide whether a criminal suspect should be charged (“indicted”) with a felony crime. Grand juries make their decision based on evidence that prosecutors present to them.1
In Colorado, the majority of criminal cases do not involve empaneling grand juries at all. Prosecutors usually decide whether or not to charge criminal suspects following a police investigation. They simply follow the standard complaint and information process.2
But in serious or high-profile cases, the District Attorney’s Office may prefer to let a group of regular citizens – the grand jury – make the charging decisions.
A grand jury can be county-wide, judicial district-wide, or statewide depending on which court has jurisdiction and the type of offense. State grand juries typically hear matters involving:
- racketeering and organized crime;
- crimes occurring in multiple judicial districts; or
- other complex cases under the state Attorney General‘s authority.
Note that defendants indicted by grand jury are not entitled to a preliminary hearing, which is where the trial judge determines if there is probable cause to prosecute the defendant. This is because grand juries and preliminary hearings serve the same purpose – deciding whether there is probable cause that the defendant committed a crime.
Defendants prosecuted through the standard complaint and information process – and not a grand jury – are entitled to a preliminary hearing.
2. How big are grand juries?
Colorado grand juries have 12 people. Nine of the grand jurors (called a “quorum“) must vote to indict for the suspect to get charged.
The District Attorney can ask the court to increase the size of a grand jury to 23 total jurors. If the court agrees, a 12-person quorum must vote to indict the suspect (“target”) to get charged.3
3. How are they different from trial juries?
The primary difference between grand juries and trial juries (also called “petit juries”) is their purpose: Grand juries decide whether a suspect should be charged with a crime. By contrast, a trial jury decides whether the defendant should be convicted of the criminal charge. In short,
- grand juries begin criminal cases, and
- trial juries end them.

Grand jury proceedings are rare in Colorado.
Ten other differences between grand- and trial juries include:
- Prosecutors use grand juries as an investigative tool to help develop evidence that the police have not been able to, often by subpoenaing witnesses or certain documents. And some of this evidence may end up being irrelevant to the case. In contrast, trial juries hear only evidence that the judge has determined is relevant. Also, hearsay evidence is admissible during grand jury proceedings but is severely limited in criminal trials.
- Grand juries and petit juries use different standards of proof to make their decisions: Grand juries must find there is probable cause to believe the suspect may have committed the crime in order to indict.4 In contrast, trial juries must find proof beyond a reasonable doubt that the defendant is guilty – that is a much higher bar than probable cause.5
- As discussed above, grand jury decisions do not have to be unanimous under Colorado law – only a quorum is necessary for the issuance of an indictment. In contrast, trial jury guilty verdicts must be unanimous.6
- Both grand jurors and trial jurors are summoned from the same pool of eligible citizens. But whereas prosecutors and defense attorneys select trial jurors during “voir dire”, grand jurors are selected by the chief judge upon the advice of prosecutors.7
- Grand jurors hear only from prosecutors and their witnesses; the suspect is not entitled to testify or call witnesses.8 Whereas during jury trials, the defendant has the right to put on a defense and testify and cross-examine state witnesses.
- Furthermore, grand jurors have the power to subpoena witnesses to testify under oath. Trial jurors do not have “subpoena power”.9
- Prosecutors have near total control of grand juries. In contrast, trial juries are guided by the judge, who has to approve every step the prosecutors make. This is another reason why it is much easier for prosecutors to get a grand jury to indict than to get a trial jury to convict.
- Grand jury proceedings are held in private, and the suspect is usually not present.10 But trials are usually open to the public, and the defendant has the right to be present.
- Unlike during trials, judges are not present during grand jury proceedings. The presiding judge’s purpose is simply to select the jury members, decide motions, and issue search warrants, arrest warrants, subpoenas, and grand jury reports or materials. And in statewide- or judicial district grand juries, the presiding judge determines the county in which an indictment will be tried.
- Finally, grand juries can be as big as 12 to 23 people. In contrast, trial juries in Colorado can be as small as three people for petty offenses and six people for misdemeanors and felonies. And the maximum size of trial juries in felony cases is 12 people.
4. What happens during grand jury proceedings?
Grand jury proceedings are like one-sided trials where only the prosecutors present evidence. During a grand jury investigation, jurors will:
- Hear evidence presented by the prosecutor (all transcribed by a certified court reporter);
- Listen to witness testimony about crimes that a third party may have committed (witnesses often include police officers, and some witnesses may testify voluntarily without having to be subpoenaed);
- Question witnesses already called;
- Subpoena additional witnesses to testify under oath if jurors find it necessary;
- Request an investigator (if necessary) to find more information;
- Review documents, testimony, or other physical evidence; and
- Convene to discuss and decide whether there is enough evidence to indict the suspect.
If the grand jury quorum decides that probable cause exists to believe the suspect committed the alleged crime, it can issue an indictment. This is also known as a “true bill” or a “presentment.” Depending on the case, grand juries can also produce an investigative report.
If the grand jury decides not to indict, it will instead issue a “no true bill” – commonly called a “no bill.”11
5. Do witnesses need to appear if they are subpoenaed?
Yes. Subpoenas are court orders. Properly subpoenaed witnesses are required to show up to the grand jury proceeding. Otherwise, the court will issue a bench warrant for the witness’s arrest. And if the witness does appear but refuses to answer questions, the court may find the witness in contempt.12 Contempt carries such penalties as fines and/or jail.13
6. Are the indictments sealed?
The district attorney may file a petition with the court requiring the court to seal the indictment. This means that no person may disclose the existence of the indictment until the defendant is in custody or has bailed out (except when it is necessary to issue or execute a summons or warrant).
Prosecutors typically ask for a seal to prevent the suspect from learning about the charges and then trying to flee or escape law enforcement. Keeping the proceeding secret also encourages witnesses to disclose the truth and promotes free deliberations in the grand jury room. Finally, secrecy
- helps prevent perjury (or subornation of perjury) and witness tampering, and
- it protects the identity of innocent people who were under investigation.14
Everyone associated with a grand jury is required to keep the proceeding secret, including:
- the jurors
- the prosecutors
- the witnesses
- the witnesses’ attorneys
- court clerks
7. How long does grand jury duty last in Colorado?
Grand juror service is for a term of 12 months, but it may be shorter if the court discharges the jurors. The term can be longer if a judge finds that it is necessary, but no term may exceed 18 months.15
8. Is the federal process different?
Grand juries are used more often in federal court than in Colorado state court. This is because federal law specifically requires grand jury indictments in all felony cases.16
Another difference has to do with size. Whereas Colorado grand juries usually have 12 jurors, federal grand juries have 16 to 23 jurors. And a quorum of 12 is always necessary to indict.17
Otherwise, the federal grand jury process is largely similar to Colorado’s.

Nine of 12 grand jurors must agree to indict a suspect for felonious criminal activity in Colorado.
9. What if I get subpoenaed to appear before a grand jury?
First, consult an attorney. An attorney can:
- Investigate the matter to determine whether you are a target of the investigation (the suspect), a subject of the investigation (someone whose conduct is within the scope of the grand jury’s investigation), or a witness (who merely may know things relevant to the investigation);
- Evaluate whether you face criminal charges, though it is rare for targets of an investigation to get a subpoena (sometimes a “target letter” is appended to a subpoena);
- Negotiate with prosecutors in an attempt to get any pending criminal case dropped and otherwise minimize exposure to criminal liability; and
- Prepare you for the grand jury proceedings by going over the facts of the case, what the proceedings will be like, and how to safeguard your rights.
Note that subpoenas ask either
- for testimony (ad testificandum),
- for documents (duces tecum), or
- for both.
Ideally, subpoenas are served upon the witness’s attorney. Getting served can be embarrassing, especially if it occurs at work. People who do get served personally should accept, tell the server if they have an attorney, and decline to say anything else.
Also note that if a law enforcement officer or an investigator with the Attorney General’s Office or U.S. Attorney’s Office contacts you by phone or knocks on your door to do a pre-grand jury interview, do not say anything. Anything you do say will be used against you and can “open new doors” of criminal liability. Retain an attorney to speak on your behalf anytime outside of the grand jury room. A witness’s attorney may be present during the grand jury proceedings that involve the witness.
10. Do I have the right to remain silent?
Everyone has the Fifth Amendment right against self-incrimination. Even grand jury witnesses who are not criminal suspects may be able to assert this federal- and state-constitutional right.
During preparation for grand jury proceedings, the witness’s attorney can help him/her determine if and when to assert the Fifth Amendment and refuse to answer the grand jury’s questions. In some cases, witnesses may assert a blanket refusal to answer all questions.
Note that every grand jury witness is placed under oath by answering “I do” to the following:
Do You Swear (Affirm), under Penalty of Perjury, That the Testimony You Are to Give Is the Truth, the Whole Truth, and Nothing but the Truth, and That You Will Keep Your Testimony Secret, Except to Discuss it with Your Attorney, or the Prosecutor, until and Unless an Indictment or Report Is Issued?
Witnesses who lie face criminal charges for perjury in the first degree (CRS 18-8-502), which is a class 4 felony punishable by
- two to six years in prison and/or
- $2,000 to $500,000 in fines.
Also note that in some cases, targets of an investigation may actually request to testify at a grand jury if they think they have exculpatory evidence that suggests they are innocent and fall outside the “spectrum of culpability”. But these targets should always consult with an attorney first about the pros and cons of testifying.
11. Can I get immunity?
Depending on the case, prosecutors may grant certain grand jury witnesses immunity from criminal charges in exchange for them testifying fully and completely.
A witness’s attorney can help broker an immunity deal ahead of time before the grand jury testimony. This would relieve the witness from having to appear twice (once to invoke their Fifth Amendment privilege, and then again to testify with immunity).
Alternatively, grand jury prosecutors can offer witnesses immunity while they are on the stand after they lawfully claim their Fifth Amendment right.
Either way, witnesses who accept immunity cannot then claim the Fifth Amendment right to remain silent. Witnesses who accept immunity but refuse to speak risk being held in contempt, which may include jail.
Note that there are two types of immunity:
- Use immunity: The testimony the witness gives in the grand jury cannot be used against him/her in future prosecutions, but the witness can still be prosecuted for any crime related to the testimony.
- Transactional immunity: The witness cannot be prosecuted for any crimes related to the testimony.
Also note that witnesses granted immunity in one jurisdiction may still be vulnerable to criminal liability in other jurisdictions depending on the case (unless they are granted “blanket inter-jurisdiction immunity”).
12. Can I challenge the grand jury indictment?
Yes. Firstly, the defendant’s attorney would make “discovery” of the grand jury proceedings by gathering all the relevant documents and evidence.
State law requires prosecutors to hand over the grand jury transcripts to the defense as soon as practicable within 30 days of the indictment. And any tangible evidence must be revealed no later than 30 days before trial.
For all other available evidence, the defense attorney must make specific requests. For instance, the defense can ask for colloquy transcripts. These document all the discussions that occurred in the grand jury room other than the testimony. The defense can also ask for any notes memos, or communications that the prosecutors have in connection to the grand jury.18
Then depending on what the defense attorney finds, the defense can file a motion to dismiss based on such arguments as:
- The prosecutors committed misconduct. This is when the prosecutors’ behavior either caused the defendant “actual prejudice” or compromised the proceedings’ integrity to the point where the court can “presume prejudice.” If the misconduct “substantially influenced the grand jury’s decision to indict”, there was prejudice.19 An example could be the prosecutor denying a witness who has exculpatory evidence from testifying. Another example is that the prosecutors’ grand jury investigators wrongly questioned the witnesses or commented on the evidence. It can also be misconduct if the prosecutors violated the grand jury’s secrecy rules.20
- The indictment was facially deficient. For example, the paperwork did not include the suspect’s name, charge, applicable statute, date and location of the offense, or language that a jury could understand. However, facial invalidity challenges are rare because prosecutors are experienced in following the sample indictment form in CRS 16-5-201.
- The indictment is not supported by probable cause. This is the most common challenge to indictments. It requires the trial court judge assigned to the criminal case (not the one who presided over the grand jury) to review the grand jury proceedings’ record in a light most favorable to the prosecution, even when there is a conflict in testimony.
- The grand jury selection process was discriminatory. It is a violation of the Sixth Amendment if the grand jury was not selected from a fair cross-section of the population.21 And it is a violation of the Equal Protection Clause of the Fourteenth Amendment if grand jurors were excluded from serving due to sex, religion, color, race, occupation, national origin, or economic status.
- A conflict of interest should disqualify the prosecutor.
If the judge agrees, the indictment could be dropped.
Our criminal law attorneys represent clients in and around Denver, Colorado Springs, Boulder County, El Paso County, Logan County, Arapahoe County, Adams County, Aurora, Fort Collins, Lakewood, Yuma, Sedgwick, Phillips County, Grand Junction, the Mesa County area, and several nearby cities. We appear in both state and federal district courts. And we defend against all types of charges from DUI, domestic violence, and drug cases to criminal impersonation, identity theft, and assault.
Legal References
- CRS 13-73-102; CRS 13-74-102; Colorado Rules of Criminal Procedure 7. See also In re 2015-2016 Jefferson Cty. Grand Jury (2018) 410 P.3d 53. See also People v. Thompson, (2008) 181 P.3d 1143.
- When a prosecutor decides to bring charges, it is called an “information.” When a grand jury decides to bring charges, it is called an “indictment.”
- CRS 13-72-102.
- CRS 16-5-204.
- CRS 18-1-402.
- See note 3; CRS 16-10-108.
- CRS 13-72-103.
- CRS 13-73-106; CRS 13-74-106.
- CRS 16-5-204.
- CRS 13-72-108; Recently in Colorado, there was a high-profile indictment that followed a secret investigation. The Colorado prosecution community was shaken when 13th Judicial District prosecutor Brittny Lewton was indicted on criminal conduct: Drug felony charges involving prescription drugs/ controlled substances. According to court records, she was also charged with official misconduct (a misdemeanor) Governor Jared Polis had appointed attorney general Phil Weiser to investigate her. Lewton’s attorney is former elected district attorney, Stan Garnett. Colleen Slevin, Colorado prosecutor indicted on drug charges, misconduct, Associated Press (February 28, 2020).
- CRS 13-73-106; CRS 13-73-107; CRS 13-74-106; CRS 13-74-107. CRS 16-5-205.5. See also Colorado Rules of Civil Procedure: Rule 6. Grand Jury Rules; Rule 6.1. Subpoenas — Issuance and Time Limits; Rule 6.2. Secrecy of Proceedings — Witness Privacy — Representation by Counsel; Rule 6.3. Oath of Witnesses; Rule 6.4; Reporting of Proceedings; Rule 6.5. Investigator; Rule 6.6. Indictment — Presentation — Sealing; Rule 6.7. Reports; Rule 6.8. Indictment — Amendment; Rule 6.9. Testimony; Rule 7. The Indictment and the Information; Rule 8. Joinder of Offenses and of Defendants; Rule 9. Warrant or Summons Upon Indictment or Information.
- CRS 13-72-204.
- Colorado Rules of Civil Procedure Rule 107. The are also alternates as well in case any of the jurors have to be dismissed.
- CRS 13-73-107; CRS 13-74-107; CRS 16-5-205.5.
- CRS 13-71-120.
- 5th Amendment to the United States Constitution.
- Federal Rules of Criminal Procedure, Rule 6.
- Colorado Criminal Rules of Procedure, Rule 16.
- Bank of Nova Scotia v. United States (1988) 487 U.S. 250.
- Colorado Criminal Rules of Procedure, Rules 6.2 and 6.5.
- Duren v. Missouri (1979) 439 US 357 (“In order to establish a prima facie violation of the fair-cross-section requirement, the defendant must show (1) that the group alleged to be excluded is a “distinctive” group in the community; (2) that the representation of this group in venires from which juries are selected is not fair and reasonable in relation to the number of such persons in the community; and (3) that this underrepresentation is due to systematic exclusion of the group in the jury-selection process.”).