Biological Evidence Preservation: Federal Rule and State Standards

Federal law and most state statutes require the government to preserve biological evidence collected in a criminal case for as long as the convicted defendant remains imprisoned, with narrow exceptions that allow earlier disposal. The federal rule is set by the Innocence Protection Act of 2004, codified at 18 U.S.C. § 3600A, and roughly 44 states and the District of Columbia have enacted their own biological evidence preservation requirements that follow a similar structure but vary in scope, duration, and the mechanics of disposal.¹

The Federal Rule Under 18 U.S.C. § 3600A

Section 3600A applies to any federal offense that results in a sentence of imprisonment. It makes no distinction among crime categories: terrorism, kidnapping, fraud, and drug offenses are treated the same way. If the conviction produces prison time, the preservation duty attaches.¹

The statute defines biological evidence as sexual assault forensic examination kits and any identified semen, blood, saliva, hair, skin tissue, or other biological material. The implementing regulations tighten that definition: the material must have been actually detected and identified as biological, not merely an item someone touched that might theoretically carry trace DNA. It also must be the kind of sample that could include or exclude the defendant as its source.²

When the Duty Starts and Ends

The federal preservation obligation begins at conviction and sentencing, not at the moment evidence is collected during investigation. Before sentencing, retention is governed by ordinary investigative and discovery practices rather than § 3600A.³

The duty ends when the defendant is released from imprisonment. The regulations are explicit on this point: the requirement “ceases to apply when the defendant or defendants are released following imprisonment” and does not extend into supervised release or parole. A sentence of probation or a fine, with no incarceration, doesn’t trigger the obligation at all. Life sentences and death sentences effectively require indefinite preservation.³

Exceptions That Allow Early Disposal

Three circumstances let the government dispose of biological evidence before a sentence ends:

After direct appeals are exhausted, the government may send the defendant written notice that the evidence will be destroyed. If no motion for DNA testing is filed within 180 days, the preservation requirement lifts.¹
When the evidence is too large or unwieldy to store, or must be returned to its rightful owner, the government may dispose of the bulk item but must take reasonable steps to extract and preserve enough biological material to allow future testing.
When evidence has already been tested under 18 U.S.C. § 3600 and the results identified the defendant as its source, the preservation obligation no longer applies.

The 180-day notice is where defendants most often lose access to evidence they might one day have wanted tested. Someone who receives the notice but doesn’t understand it, or whose mail is delayed in a prison system, can forfeit any future testing simply through inaction.

Guilty Pleas and DNA Testing Waivers

A guilty plea by itself does not eliminate the preservation requirement. The federal duty applies to any case resulting in imprisonment, whether the conviction came from trial or plea. But if a defendant knowingly and voluntarily waives DNA testing in a court proceeding conducted after October 30, 2004, the preservation requirement drops away. That waiver can appear in a plea agreement, a pretrial colloquy, discovery, or a post-conviction proceeding.⁴ Defendants negotiating pleas should check whether such a waiver is included, because signing it allows the evidence to be destroyed.

What Counts as Biological Evidence

At the federal level, the covered categories are sexual assault examination kits and identified biological material: semen, blood, saliva, hair, skin tissue, and similar organic matter.¹ Many state statutes use parallel definitions and some add fingernail scrapings, bone, and bodily fluids.⁵

Preservation also reaches items that carry biological traces, including clothing, bedding, and weapons. Those items can be retained whole or sampled, so long as enough material is preserved to allow future testing. The federal regulations draw a limit, though: the duty covers material actually detected and identified as biological. The theoretical possibility that an object carries imperceptible DNA is not enough.²

How States Differ

State preservation laws form a patchwork. The crimes that trigger retention, the length of time evidence must be kept, and who carries the burden of making sure it survives all vary. A handful of states still have no dedicated statute.

California’s Penal Code § 1417.9 requires the appropriate governmental entity to retain all biological material connected to a criminal case for the entire period any person remains incarcerated in that case. Before disposing of material, the government must notify any incarcerated person serving time for a felony conviction in the case and give them an opportunity to object.⁶

Texas uses a different structure in Article 38.43 of the Code of Criminal Procedure. The preservation duty covers biological evidence from the investigation or prosecution of any felony. For capital felonies, evidence must be kept until the inmate is executed, dies, or is released on parole. For other felonies resulting in imprisonment, the duty continues until the defendant dies, completes the sentence, or is released on parole or mandatory supervision.⁵

Some states impose the preservation duty automatically on custodial agencies. Others place the burden on the prisoner to file a motion requesting that evidence be preserved, which means an uninformed defendant can lose access to potentially exculpatory material by not knowing to ask. Treatment of guilty pleas also differs. In some states a plea has no effect on preservation; in others, waiver can be built into the agreement. A few states impose fixed retention periods — 25 or 50 years, for example — running from the date of final conviction, regardless of the sentence length. A pending motion for DNA testing or a post-conviction appeal typically freezes disposal until the proceedings conclude.

Storage Standards for Custodians

Law enforcement agencies, crime laboratories, and court clerks are the primary custodians. They must store biological evidence in conditions that prevent DNA from degrading beyond usefulness. The National Institute of Standards and Technology has published best practices with recommended environmental ranges:

Frozen storage at or below –10°C (14°F), suitable for samples that may need the most sensitive future analysis.
Refrigerated storage between 2°C and 8°C (36°F to 46°F), with humidity below 25%.
Temperature-controlled storage between 15.5°C and 24°C (60°F to 75°F), with humidity below 60%.

NIST’s core guidance is that DNA keeps best in an air-dried, water-free environment, because moisture breaks down DNA strands and encourages mold and bacterial growth.⁷

There is no federal mandate requiring evidence storage facilities to be accredited. Accreditation to ISO/IEC 17020 for inspection bodies or ISO/IEC 17025 for testing laboratories is voluntary in the United States. Some states and accrediting bodies add their own requirements, but a uniform national quality standard does not exist.⁸

Custodial agencies must maintain a clear chain of custody documenting who handled the evidence and where it was stored. Before any disposal, notification procedures apply. At the federal level, the Special Agent in Charge must provide written notice to the relevant U.S. Attorney’s Office before any disposal begins, and if a defendant or attorney objects, the agency must continue storing the material until a court resolves the dispute.⁹

Penalties for Destroying Preserved Evidence

Under 18 U.S.C. § 3600A(f), anyone who knowingly and intentionally destroys, alters, or tampers with biological evidence required to be preserved, with the intent to prevent DNA testing or block its use in an official proceeding, faces up to five years in prison and a fine. The statute also directed the Attorney General to adopt regulations imposing disciplinary sanctions on employees who fail to comply with preservation requirements.¹

Criminal penalties aside, destruction of evidence can affect the underlying case. Courts may issue adverse inference instructions telling jurors they can assume the destroyed evidence would have been unfavorable to the party that destroyed it. In the most serious cases, a court can dismiss charges or vacate a conviction.

The Due Process Standard

Two Supreme Court decisions govern constitutional claims when biological evidence is lost or destroyed. In California v. Trombetta (1984), the Court held that the government has a duty to preserve evidence that might play a significant role in a suspect’s defense. The evidence must have had an apparent exculpatory value before destruction, and the defendant must be unable to obtain comparable evidence through other means.¹⁰

Arizona v. Youngblood (1988) set a higher bar for evidence that is only “potentially useful” rather than clearly exculpatory. Failure to preserve such evidence does not violate due process unless the defendant can show bad faith by the police. Negligent loss or sloppy handling alone is not a constitutional violation.

These cases create a two-track analysis. Clearly exculpatory evidence doesn’t require bad faith; potentially useful evidence does. Most biological evidence falls into the second category, and proving what a police department was thinking when it cleaned out a storage locker is difficult.

Using Preserved Evidence: Post-Conviction DNA Testing

Preservation laws exist so that post-conviction DNA testing remains possible. Under 18 U.S.C. § 3600, a federal prisoner can file a written motion asking a court to order testing of specific evidence. The applicant must assert actual innocence under penalty of perjury, identify the specific evidence, propose scientifically sound methods, and explain how favorable results would establish innocence. Additional requirements apply: the evidence must not have been previously tested (unless a newer, substantially more probative method is requested), the chain of custody must be intact, the identity of the perpetrator must have been contested at any trial, and the applicant must agree to provide a DNA sample for comparison.¹¹

A rebuttable presumption of timeliness applies when the motion is filed within 36 months of conviction. Motions filed later face a presumption against timeliness, which can be overcome by showing newly discovered evidence, manifest injustice, or other good cause. Indigent applicants may receive court-appointed counsel.¹²

1
Office of the Law Revision Counsel. 18 USC 3600A – Preservation of Biological Evidence
2
eCFR. 28 CFR 28.23 – Scope of the Evidence Preservation Requirement
3
eCFR. 28 CFR 28.22 – Scope of the Preservation Requirement – Duration
4
eCFR. 28 CFR Part 28 Subpart C – Preservation of Biological Evidence – Section 28.25
5
Texas Legislature Online. Texas Code of Criminal Procedure – Art 38.43
6
Justia. California Code Penal Code 1417-1417.9
7
National Institute of Standards and Technology. The Biological Evidence Preservation Handbook – Best Practices for Evidence Handlers
8
National Institute of Standards and Technology. Demystifying Accreditation – A Framework for Accreditation of Forensic Units
9
U.S. Department of Justice. Justice Manual 9-14.000 – Procedure for Disposal of Seized Evidence in Closed Criminal Cases
10
Justia. California v. Trombetta, 467 US 479 (1984)
11
Office of the Law Revision Counsel. 18 USC 3600 – DNA Testing
12
Office of the Law Revision Counsel. 18 USC Chapter 228A – Post-Conviction DNA Testing