Chain of custody refers to the documentation that tracks the control, transfer, testing, and storage of evidence in a criminal case. In Wyoming and South Dakota, this process is governed by each state’s rules of evidence and police agency protocols. Evidence may include DNA samples, photographs, documents, personal items, drugs, weapons, or bodily fluids taken from a defendant or collected at the scene of an alleged crime.
To prove someone guilty, a prosecutor in Wyoming or South Dakota must show that the evidence presented in court is the same evidence recovered at the scene and that it was handled properly. If the chain of custody is incomplete, unclear, or mishandled, the defense can challenge the evidence on grounds of contamination, tampering, or misidentification.
Because criminal prosecutions in both states rely heavily on evidence gathered by law enforcement, it is the prosecutor’s burden to establish a proper chain of custody.
Proving chain of custody can be difficult, especially in cases involving multiple officers, labs, or transfers between agencies such as the Wyoming State Crime Laboratory or the South Dakota State Forensic Laboratory. Mistakes can—and often do—occur. When they do, the chain of custody can be challenged. A successful challenge can result in key evidence being suppressed, which may dramatically weaken the prosecution’s case.
A defense lawyer who successfully challenges chain of custody can request that the evidence be excluded. If the judge finds the evidence inadmissible, the prosecutor may no longer have a viable case.
Why Is Chain of Custody Important in a Criminal Case?
Judges and juries in Wyoming and South Dakota can only rely on the evidence that is properly admitted into the courtroom. They are not allowed to conduct their own investigation or speculate about missing information. If the evidence has been mishandled, mislabeled, contaminated, or tampered with, it undermines the integrity of the entire case.
Chain of custody issues often arise in:
- Drug cases (methamphetamine, marijuana, cocaine, prescription pills)
- DUI and DWUI cases involving blood or breath samples
- Gun and weapons cases
- Sexual assault cases involving biological evidence
- Any case involving forensic lab testing
To establish chain of custody, prosecutors must show through testimony and documentation that the item presented at trial is the same item seized from the defendant or crime scene—and that it was preserved in substantially the same condition.
In a typical Wyoming or South Dakota case, a police officer collects the evidence and transfers it to a forensic technician or evidence custodian. Technicians may test the evidence—such as analyzing a blood-alcohol sample or confirming a substance is an illegal drug. All tests must be documented. Once analysis is complete, the item is stored in the agency’s evidence facility until it is needed again.
What Is Included in an Evidence Log?
For chain of custody to be proven, law enforcement must be able to identify exactly who had control of the evidence at all times. This is done through an evidence log, often required by agency policy and used statewide.
A proper evidence log should include:
- Date and time the evidence was collected
- Name of the investigator or officer
- Exact location where it was collected
- Reason it was collected
- Serial numbers or identifying information
- A detailed description of the evidence
- The method of collection
- Signatures of every person who handled or transferred the evidence
- Dates and times of each transfer
- How the evidence was stored and secured
Any time a forensic examiner tests the evidence, they must document what tests were performed and every person who handled the evidence during the process.
Challenging Chain of Custody in a WY or SD Criminal Case
A defendant can challenge chain of custody by questioning whether the evidence presented in court is actually the same item collected at the scene. This is a common and often effective defense strategy in both Wyoming and South Dakota courts.
If there are discrepancies in the chain—missing signatures, unexplained gaps in time, improper labeling, incorrect packaging, or failure to follow agency protocol—the defense can argue that the chain of custody was broken. If the judge agrees, the evidence may be declared inadmissible.
To establish chain of custody, prosecutors must prove:
- The evidence is what they claim it is (e.g., the substance is actually methamphetamine, or the blood sample came from the defendant).
- Continuous possession of the evidence from seizure to trial.
- No material changes occurred to the evidence during handling or testing.
The chain can be broken if a form is mislabeled, if transfers take too long without explanation, or if mishandling suggests tampering or contamination.
Even when a judge allows the evidence in, the defense can still use chain-of-custody problems to argue that the evidence is unreliable—undermining the prosecution’s case in the eyes of the jury.
Just Criminal Law Protects Your One Shot at Justice
If you have been charged with a crime in Wyoming or South Dakota, the chain of custody may be a critical issue in your case. Our team knows how to identify weaknesses in the prosecution’s evidence—and how to use those weaknesses to protect your rights.
Learn more about our founding attorney, Christina L. Williams, our team of criminal defense professionals, the types of cases we handle, and why clients across Wyoming and South Dakota choose us. Then contact Just Criminal Law today to schedule your personalized case review and strategy session.