Title: Preservation of Evidence in Criminal Cases | Nolo
Headings: Preservation of Evidence in Criminal Cases
Preservation of Evidence in Criminal Cases
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.
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What Kind of Evidence Must Be Preserved?
Alibi evidence
Other kinds of evidence
Who Has to Preserve Evidence?
Private people exempted
What Happens If Evidence Is Lost or Destroyed?
Proving materiality
Proving bad faith
Remedies

Content: 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.