Preservation of Evidence in Criminal Cases

Posted by Chris Morales on Fri, Aug 21, 2015 @ 09:00 AM

Law enforcement officers and prosecutors have a duty to preserve certain kinds of evidence. Learn what they have to keep, and what happens when they don't keep it.

The government has a duty to preserve certain types of evidence it collects during criminal investigations and prosecutions. This duty exists in order to protect a defendant’s rights to due process and a fair trial under the Sixth and 14th Amendments to the U.S. Constitution. The duty relates to the requirement that the government disclose evidence it will use against the defendant at trial, as well as any evidence that is favorable to the defendant. The duty to preserve evidence begins once any state agency or actor has gathered and taken possession of evidence as part of a criminal investigation.

What Kind of Evidence Must Be Preserved?

Law enforcement doesn’t need to preserve all evidence it collects. The duty to preserve extends only to evidence that might be expected to play a significant role in the suspect’s defense: “material” and “exculpatory” evidence. Material evidence is important evidence that’s directly relevant to an issue in the defendant’s case. Exculpatory evidence is evidence favorable to the defendant in that it clears or tends to clear him of guilt.

Alibi evidence

Exactly what evidence is material and exculpatory depends upon the circumstances of the case. But alibi evidence is virtually always material and exculpatory; it includes witness statements that place the defendant somewhere other than the scene of the crime and forensic evidence (like DNA) that tends to show that the defendant couldn’t have committed the crime.

Other kinds of evidence

In many cases, law enforcement doesn’t have obvious alibi evidence, but it does have other kinds of material and exculpatory evidence. An example is evidence that impeaches the prosecution's witnesses or otherwise weakens its case. Such evidence may include:

  • Crime scene evidence. Most jurisdictions have local and state rules about the collection and preservation of evidence at the crime scene, such as the murder weapon, blood samples, and photographs of the scene.
  • Tape recordings and videotapes. The police usually aren’t required to tape record statements of the defendant or witnesses. However, if they do make audio or video recordings of statements, they have to preserve them.
  • Investigative notes. Most states require officers and investigators to preserve investigative notes only if they made them during an interrogation of the defendant. (But if those notes contain exculpatory information, that information must be conveyed to the defense.)
  • Emergency call recordings. Law enforcement typically must preserve and disclose 911 recordings (or transcripts of the calls) to the defendant.

Who Has to Preserve Evidence?

While the police typically collect most evidence used in a criminal case, they aren’t the only government actors who have to preserve evidence. The duty also extends to:

  • Local, county, and state investigative agencies. These include not just detectives and investigators, but also administrative, clerical, and forensic staff.
  • Prosecutors. The attorneys prosecuting the case have an obvious duty to preserve evidence, as do people acting under prosecutorial authority (for example, investigators or experts retained by the prosecutor’s office).
  • The Attorney General. In most states and in most cases, the duty to preserve evidence remains even after a defendant has been convicted. Therefore, the duty applies to a state’s Attorney General’s office (which typically handles appeals and post-conviction matters).

Private people exempted

The duty to preserve evidence doesn’t extend to private people or agencies unless they have a formal relationship with a law enforcement agency. Thus, if a private DNA lab is hired by the prosecutor to examine blood samples collected from a crime scene, that lab must protect and preserve the evidence and the results of any testing it conducts on the evidence.

What Happens If Evidence Is Lost or Destroyed?

Defendants have the burden of proving that the state violated its duty to preserve evidence, and that that violation compromised the rights to due process and a fair trial. Courts won’t do anything about an alleged violation unless the defendant proves that the evidence in question was material and potentially exculpatory and that the government acted in bad faith. In practice, it’s very difficult to prove these points.

Proving materiality

In order to prove that the evidence was material, the defendant must establish that

  • law enforcement officers had reason to believe the evidence was exculpatory before they destroyed it, and
  • the evidence can’t be replaced by other reasonably available evidence.

Courts can sometimes infer materiality from law enforcement’s actionsFor example, the fact that the state normally preserves the type of evidence that it destroyed in the defendant’s case may show that the evidence was material. Similarly, the government testing, using, or intending to test or use the evidence provides a strong indication that it recognized the importance of that evidence.

Proving bad faith

Proving bad faith is tough. It’s not enough that government actors were careless or negligent with the evidence—the defendant must show willful, deceitful, or malicious intent. The government failing to follow standard procedures when it lost or destroyed evidence can support an inference of bad faith. An example of bad faith is an officer throwing away a fingerprint sample showing that someone other than the defendant committed the crime.


There are several possible remedies for defendants who learn during trial that the state violated the duty to preserve evidence. They can ask the court to suppress related evidence, exclude or limit testimony about the missing evidence, or dismiss the case. If the missing evidence doesn’t surface until after a conviction, overturning the conviction and obtaining a new trial on appeal are possible.

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Tags: prosecutors, evidence, law enforcement, criminal case, officers, rights

Criminal Charges: How Cases Get Started

Posted by Chris Morales on Fri, Jun 19, 2015 @ 07:10 AM

How police officers and prosecutors initiate criminal cases.

A criminal case usually gets started with a police arrest report. The prosecutor then decides what criminal charges to file, if any. Some cases can then go to a grand jury for a criminal indictment or to a preliminary hearing, where a judge decides if there is enough evidence to proceed. Here's how this all works.

Arrest Reports and Criminal Charges

After an arrest, the police report goes to a prosecutor, whose job it is to initiate and prosecute cases. An arrest report summarizes the events leading up to the arrest and provides numerous details, such as dates, times, locations, and witness names and addresses (if available).

The prosecutor will typically either:

  • determine that the case should be charged (as a felony or a misdemeanor), and file a “complaint” (the charging document may go by a different name) with the court
  • decide that the case would be a felony and should go to a grand jury, which will decide what charges, if any, to file, or
  • decide not to pursue the case.

A police officer specifies the crime or crimes that serve(s) as the basis for an arrest. Officers may recommend that the prosecution file additional charges, too. But prosecutors get to make the ultimate decision on what the charges will be. (See How do prosecutors decide whether to file criminal charges?)

A defendant typically learns what the formal charges will be at the first court appearance. To learn about that appearance, and how quickly after arrest it must occur, see Arraignment: Getting to Court.

Keep in mind that prosecutors' initial charges are subject to change. For example, a prosecutor may not make a final decision on what charges to file until after a preliminary hearing, which may take place more than a month after arrest.

The Role of a Grand Jury

If a felony is involved, prosecutors sometimes leave it to grand juries to decide whether charges should be filed. Grand juries are similar to regular trial juries (called "petit juries") in that they are made up of randomly selected individuals. The grand jurors listen to evidence and decide whether charges should be brought against an individual—that is, they decide whether to "indict" someone.

However, unlike petit juries, which sit only on one case, grand juries involve a time commitment that typically lasts between six and 18 months. The grand jurors may address many cases in the course of their service. In addition, these crucial differences exist:

  • Petit jurors decide whether defendants are guilty. Grand juries decide whether there is enough evidence to warrant a trial.
  • Grand juries meet in secret proceedings. Petit juries serve during public trials.
  • Grand juries tend to be bigger than petit juries. In federal court, for example, they consist of 16 to 23 people. By contrast, a petit jury usually comprises six to 12 people.
  • Petit juries generally have to be unanimous to convict a defendant. (But see Do criminal jury verdicts have to be unanimous?) Grand juries need not be unanimous to indict. In the federal system, for example, an indictment may be returned if 12 or more jurors agree to indict.

How a Grand Jury Works

When a prosecutor brings a case to a grand jury, he presents the jurors with a "bill" (the charges) and introduces evidence—usually the minimum necessary, in the prosecutor's opinion—to secure an indictment. The proceedings are secret; it is standard practice to call witnesses to testify against the suspect without the suspect or the suspect's lawyer present. But indicted suspects can sometimes later obtain transcripts of grand jury proceedings; the availability of a transcript is a big reason why prosecutors like to keep the evidence to the minimum.

Although prosecutors can also call suspects as witnesses, they typically don’t. When suspects are called, they often refuse to testify by invoking their privilege against self-incrimination under the Fifth Amendment to the U.S. Constitution.

If the grand jury decides to indict, it returns what is called a "true bill." If not, the grand jury returns a "no bill". But even if the grand jury returns a no bill, the case isn’t always closed. Prosecutors can return to the same grand jury with more evidence, present the same evidence to a second grand jury, or (in jurisdictions that give prosecutors a choice) bypass the grand jury altogether and file a criminal complaint.

How a Preliminary Hearing Works

Typically, if the prosecutor decides to file a complaint rather than present the case to a grand jury, and the case is a felony, the defendant is entitled to a preliminary hearing. At that hearing, the prosecutor must show that the state has enough evidence of the crime to warrant a trial.

But normally, if the case proceeds by grand jury indictment, no preliminary hearing need be held.

For much more on this stage of a case, see our section on Preliminary Hearings.

Get a Lawyer

Charging procedure differs significantly between federal and state court, from one state to another, and even between locales within the same state. If you’ve been arrested, consult an experienced criminal defense attorney. Such a lawyer will be able to fully explain the applicable law and guide you through the process. You can check out Nolo's trusted Lawyer Directory to find a criminal defense attorney in your area.

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Tags: Criminal Charges, grand jury, preliminary hearing, officers, arrest reports, police

Indiana woman stripped by jailers and left naked for 7 hours

Posted by Chris Morales on Fri, Jun 13, 2014 @ 02:59 PM

An Indiana woman arrested for a misdemeanor resulted in her being stripped naked, pepper-sprayed and left for hours on the floor of an unsanitary holding cell, according to her attorney.

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Tags: misdemeanor, dispute, pepper-sprayed, video, officers, stripped