Your arrest report indicates 0.12% blood alcohol content. That single figure carries enormous weight in your DUI case, but behind that number sits a certificate of analysis. The process to create this document isn't always as reliable as prosecutors want you to believe.
A Chesapeake DUI defense attorney knows that certificates of analysis must meet specific legal requirements to be admissible in Virginia courts. Lab technicians make mistakes. Equipment malfunctions. Chain of custody breaks. When these failures happen, the evidence against you becomes vulnerable to challenge.
What Is a Certificate of Analysis in a DUI Case?
A certificate of analysis (COA) is the official laboratory report documenting results from either a breath or blood test. Under Va. Code § 19.2-187, certificates of analysis may be admissible if filed with the clerk and noticed as the statute requires. The certificate is used by the Commonwealth to prove the reported alcohol or drug result.
Blood Tests
For blood alcohol testing, the certificate must state:
- The time the sample was received and examined
- The seal was not broken or tampered with
- A Department of Forensic Science-approved vial was used
- A properly executed withdrawal certificate was attached
Blood samples are drawn at medical facilities or jails under strict protocols, then transported to state laboratories for testing using validated laboratory methods.
Breath Tests
For breath testing, evidential tests (not preliminary roadside screening devices) follow protocols established by the Department of Forensic Science. Breath test evidence requires DFS-approved equipment operated by certified personnel using approved methods. These evidential breath tests typically occur at police stations.
Virginia's Notice and Objection Requirements
The Commonwealth must provide notice of its intent to introduce a certificate generally at least 28 days before trial or hearing, excluding preliminary hearings. Once the Commonwealth files the certificate and notice with the clerk, you must file a written objection within 14 days if you want to demand the analyst appear as a witness. Miss this deadline, and you waive your confrontation rights.
This notice-and-demand system means you cannot simply object at trial.
The objection must be filed in writing well before your court date. Separately, the Commonwealth may provide notice of its intent to offer the analyst's testimony via two-way video. You retain the legal right to object to that procedure.
Your Right to Confront the Analyst
The U.S. Supreme Court ruled in Melendez-Diaz v. Massachusetts that certificates of analysis are testimonial evidence. This means you have the constitutional right to cross-examine the analyst who prepared the report.
Prosecutors sometimes try to present a supervising analyst who didn't perform your specific test, but this violates your confrontation rights when properly objected to under the procedures above. The court may suppress the BAC evidence if the analyst fails to appear, which may significantly weaken the prosecution's case against you.
How Lab Errors Invalidate Test Results
Forensic laboratories process thousands of samples under pressure to deliver results quickly. This environment creates opportunities for mistakes that can corrupt your test results.
Common laboratory errors include:
- Contaminated samples. When labs use expired collection tubes or improper additives, bacterial action can create alcohol that wasn't in your blood at collection.
- Failed accuracy testing. Virginia breath-test device regulations require that devices be tested for accuracy at least once every six months.
- Sample mix-ups. Busy labs sometimes mislabel vials or transpose results between different defendants' samples. Your certificate might actually reflect someone else's BAC.
Challenging Chain of Custody and Sample Integrity
Chain of custody tracks your blood sample from collection through analysis to ensure no tampering or mix-up occurred. The chain starts when a qualified medical professional draws your blood and seals the vial with your identifying information.
That vial must remain sealed until the lab analyst opens it for testing. Every transfer between people, from nurse to police officer to evidence technician to lab courier to analyst, should be documented with dates, times, and signatures. Each undocumented transfer creates an opportunity for sample switching or contamination.
Your Right to Independent Testing
Virginia provides a mechanism for you to request transmission of the remaining blood sample to an independent laboratory. Blood samples are held for 90 days to allow defendants to file a motion for independent testing. You must file this motion before the 90-day period expires. Independent testing gives you comparison results that may contradict the state's certificate.
When independent results show a significantly lower BAC than the state's test, this discrepancy creates reasonable doubt. The jury must decide which test to believe, and any doubt works in your favor since the prosecution must prove guilt beyond a reasonable doubt.
When Certificates May Be Excluded or Challenged
Judges may exclude certificates of analysis when confrontation rights are properly asserted and the analyst cannot testify, when chain of custody breaks cannot be explained, or when laboratory errors cast doubt on accuracy. Successful challenges to certificates can lead to suppression of BAC evidence, which may result in charge dismissals or favorable plea agreements, depending on the remaining evidence in your case.
Attorney James Short began his career prosecuting DUI cases as an Assistant Commonwealth's Attorney for the City of Portsmouth. Since entering private practice in 1991, he has defended hundreds of DUI cases throughout Chesapeake, Portsmouth, Norfolk, Suffolk, and Virginia Beach. This experience from both sides of the courtroom provides insight into how to challenge certificates of analysis and the laboratory evidence behind them.
If you're facing DUI charges in Virginia, contact our office to discuss how we can examine the certificate of analysis in your case and develop a defense strategy that protects your rights under Virginia's notice and objection procedures.