How Long Do Police Keep DUI Blood Samples in California?
If you were arrested for DUI in California and provided a blood sample, you may be wondering what happens to that sample after it is collected. Is it destroyed after testing? Can it be retested? How long is it kept?
These are important questions because blood evidence often plays a significant role in DUI cases. Unlike a breath test, a blood sample may be available for independent testing by the defense. That makes preserving the sample, and understanding how long it may be retained, an important part of protecting your rights.
The answer, however, is not as simple as a single statewide rule. The amount of time a DUI blood sample is kept can vary depending on the laboratory, the agency involved, and the circumstances of the case.
Why Are Blood Samples Collected?
California law enforcement officers may request a blood sample when they believe a driver was impaired by alcohol, drugs, or a combination of both. Blood testing is especially common when:
- A driver is suspected of driving under the influence of drugs.
- A breath test is unavailable or impractical.
- The case involves an accident with injuries.
- A search warrant authorizes a blood draw.
- Additional forensic testing may be necessary.
How Long Are DUI Blood Samples Usually Kept?
There is no single California law requiring every laboratory to retain DUI blood samples for a specific length of time.
Instead, retention periods are often determined by:
- The policies of the crime laboratory that analyzed the sample
- The law enforcement agency involved
- Whether criminal charges are pending
- Whether appeals or additional testing may still occur
- Evidence retention requirements established by local agencies
Many laboratories retain samples for months or even years, particularly while a criminal case remains active. However, once legal proceedings have concluded and any applicable retention period has expired, the sample may eventually be destroyed according to established evidence procedures.
Because policies vary, it is important not to assume a blood sample will always remain available indefinitely.
Why Blood Sample Preservation Matters
One of the biggest advantages of blood evidence is that it can often be independently analyzed.
An experienced DUI defense attorney may request that a portion of the blood sample be preserved for testing by an independent forensic laboratory. This independent analysis may help determine whether the government’s test results are accurate.
In some cases, additional testing may reveal issues involving:
- Laboratory error
- Sample contamination
- Improper storage
- Fermentation
- Problems with preservatives
- Chain of custody concerns
- Inaccurate blood alcohol calculations
Can a Blood Sample Be Retested?
Unlike breath tests, which generally cannot be recreated after they are administered, blood samples often allow for additional testing if enough of the sample remains. Defense experts may examine:
- Blood alcohol concentration
- Testing methodology
- Laboratory procedures
- Instrument calibration
- Sample integrity
- Presence of medications or other substances
Retesting does not automatically mean the original results were wrong, but it can provide valuable information about the reliability of the evidence.
What Is the Chain of Custody?
Every blood sample should be carefully documented from the moment it is collected until it is analyzed and stored. This documentation is known as the “chain of custody.”
It records who handled the sample, when it changed hands, where it was stored, and how it was transported.
If there are unexplained gaps in the chain of custody, the defense may question whether the sample remained secure and whether the test results should be considered reliable.
Can Improper Storage Affect the Results?
Blood samples must be collected, preserved, transported, and stored according to accepted forensic procedures.
Improper handling may contribute to issues such as:
- Degradation of the sample
- Contamination
- Incorrect preservation
- Problems with refrigeration
- Fermentation that may affect alcohol readings
Should You Wait Before Requesting Retesting?
If independent testing may be appropriate, it is usually better to act sooner rather than later. Waiting too long could create complications if:
- The sample is no longer available.
- The laboratory’s retention period expires.
- Additional degradation occurs over time.
- Important records become more difficult to obtain.
An attorney can take steps to request the necessary records and, when appropriate, arrange for independent testing before evidence is no longer available.
Does Every DUI Case Need Independent Blood Testing?
Whether independent testing makes sense depends on the facts of the case. An attorney may consider factors such as:
- The reported BAC level
- Whether drugs were allegedly involved
- The circumstances of the traffic stop
- Possible laboratory issues
- Other available evidence
- The overall defense strategy
In some cases, independent testing may provide valuable insight. In others, different legal issues may be more significant.
Why an Experienced DUI Attorney Matters
Blood evidence often appears scientific and difficult to challenge, but that does not mean it is beyond question.
Experienced DUI attorneys understand how blood evidence is collected, analyzed, and preserved. They know what records to obtain, when independent testing may be appropriate, and how to identify issues involving laboratory procedures, chain of custody, or evidence handling.
Carefully reviewing blood evidence can uncover weaknesses that might otherwise go unnoticed.
San Diego DUI Lawyer
If your DUI case involves a blood test, time can be an important factor. The longer you wait, the greater the possibility that evidence may become more difficult to review or independently analyze.
Rick Mueller has extensive experience defending DUI cases throughout San Diego County, including cases involving blood alcohol testing and forensic evidence. He carefully evaluates every aspect of the prosecution’s case, including laboratory procedures, evidence preservation, and the handling of blood samples, to identify opportunities to challenge the evidence whenever appropriate.
If you have been arrested for DUI, contact Rick Mueller today for a confidential consultation to discuss your case and your legal options.
How Long Do Police Keep DUI Blood Samples in California?