Preserving Evidence in Criminal Law Cases
Since a criminal case involves very high stakes, a defendant has a right to a fair trial under the Sixth Amendment to the Constitution. Among other things, this right requires the prosecution to preserve certain evidence obtained during its investigation of the case. During a process known as discovery, it must provide the defendant with the evidence that it will use in presenting its case. The prosecution also must provide the defendant with exculpatory evidence that could support a defense. This is because the prosecutor’s duty is to obtain justice rather than simply obtaining a conviction.
The evidence that must be preserved is limited to evidence that would be both material and exculpatory. Evidence is material if it is relevant to an important issue in the case, and evidence is exculpatory if it supports a defense or tends to show that the defendant is not guilty of the crime.
Types of Evidence to Preserve
One of the most common types of exculpatory evidence is evidence that supports an alibi. This could consist of any statements or materials that suggest that the defendant was not in the location where the crime was committed at the time that it was committed or otherwise could not have committed the crime.
Other types of exculpatory evidence might consist of recorded statements of the defendant or witnesses, as well as recordings of 911 calls. It also might involve photographs, blood samples, and other tangible evidence from the scene of the crime. In some cases, law enforcement may need to preserve notes of their investigation, but this duty may extend only to notes that record an interrogation of the defendant.
A defendant may file a Motion to Preserve Evidence to examine or test evidence themselves. For example, a prosecution expert evaluates DNA evidence and concludes that the DNA matches the defendant. The defendant then asks the judge to preserve the DNA evidence so that the defendant may hire their own expert to conduct testing.
Agencies Responsible for Preserving Evidence
A private person or entity does not have an obligation to preserve evidence, unless they were formally working for or with a law enforcement agency. (An example might be a scientific lab that is regularly retained by the prosecutor’s office to examine evidence.) However, most government agents have a responsibility to preserve evidence. These range from police and prosecutors to detectives and investigators working for the prosecutor’s office, administrative staff, and the Attorney General’s Office. The duty to preserve evidence starts as soon as the evidence is obtained and continues after a conviction to cover any exculpatory evidence that might assist a defendant in an appeal.
Consequences of Losing or Destroying Evidence
A court will not sanction the prosecution on its own if the prosecution loses or destroys evidence. A defendant or their attorney will need to raise the issue. They will need to show that the government acted in bad faith in violating the duty to preserve evidence, and they also need to show that the evidence was material and exculpatory, such that their right to a fair trial was violated. If the defendant succeeds, the court might suppress the related evidence or limit testimony about it. In some extreme cases, the court might even dismiss the case. If the issue does not arise until after a conviction, an appellate court might overturn the conviction and order a new trial.
Proving bad faith requires showing intentional misconduct by the government, rather than mere carelessness. A failure to follow procedures can suggest bad faith, but it is a challenging standard to meet.
Proving that the evidence was material requires showing that the government should have known that the evidence was exculpatory. The defense also needs to show that no other available evidence could have served the same purpose. If the prosecution usually preserves the evidence that was destroyed, or if it had planned to analyze this evidence, this suggests that it knew that the evidence was material.
Criminal Law Center Contents
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Criminal Law Center
- Aggravating and Mitigating Factors in Criminal Sentencing Law
- Bail, Bonds, and Relevant Legal Concerns
- Restitution for Victims in Criminal Law
- Plea Bargains in Criminal Law Cases
- Receiving Immunity for Testimony in a Criminal Law Case
- Legal Classification of Criminal Offenses
- Common Criminal Defenses
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Criminal Procedure Law
- Admissibility of Evidence in Criminal Law Cases
- Criminal Appeals
- Motions for a New Trial in Criminal Law Cases
- Competency to Stand Trial in Criminal Law Cases
- Continuances in Criminal Law Cases
- Judgments of Acquittal in Criminal Trials
- Joint Trials for Criminal Defendants & Legal Considerations
- Immigration Removal Proceedings & Criminal Law Concerns
- Miranda Rights for Criminal Suspects Under the Law
- Police Stops on the Street & Your Legal Rights
- Video or Audio Recording of Police Officers & Your Legal Rights
- Arrests and Arrest Warrants
- Constitutional Rights in Criminal Law Proceedings
- The Right to a Speedy Trial in a Criminal Law Case
- The Right to a Public Trial in a Criminal Law Case
- Double Jeopardy & Legal Protections for Criminal Defendants
- Discovery in Criminal Law Cases
- Hearsay Evidence in Criminal Law
- Stages of a Criminal Case
- Stages of a Criminal Trial
- The Search Warrant Requirement in Criminal Investigations & Legal Exceptions
- Limits on Searches and Seizures in Criminal Investigations by Law Enforcement
- Qualified Immunity
- Criminal Statutes of Limitations: 50-State Survey
- Types of Criminal Offenses
- Alcohol Crimes Under the Law
- Parole and Probation Law
- Expungement and Sealing of Criminal Records
- Offenses Included in Other Crimes Under the Law
- The Mental State Requirement in Criminal Law Cases
- Derivative Responsibility in Criminal Law Cases
- Working with a Criminal Lawyer
- Criminal Law FAQs
- Domestic Violence Restraining Orders Laws and Forms: 50-State Survey
- Abortion Laws: 50-State Survey
- Gun Laws: 50-State Survey
- Hate Crime Laws: 50-State Survey
- Death Penalty Laws: 50-State Survey
- Recording Phone Calls and Conversations Under the Law: 50-State Survey
- Criminal Law Topics
- Find a Criminal Law Lawyer
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