A blood result can look conclusive on an arrest report: a number, a decimal point, and an allegation that the driver was over the legal limit. But a DUI blood test review is not limited to reading that number. It means examining how the sample was obtained, handled, tested, reported, and connected to the driving that led to the arrest. In a Los Angeles County DUI case, those details can affect the evidence the prosecutor can use and the defense strategy from the beginning.
A person accused of DUI should not try to explain the result to police, an insurance company, or anyone else investigating the incident. Exercise the right to remain silent and speak with counsel before making statements. The laboratory record may be important, but it is only one part of the case.
What a DUI Blood Test Is Supposed to Prove
California prosecutors commonly use blood testing to pursue an alcohol DUI under Vehicle Code section 23152(b), which prohibits driving with a blood-alcohol concentration of 0.08% or more. Blood evidence may also be used in cases involving alleged drug impairment under sections 23152(f) and 23152(g).
A reported blood-alcohol concentration does not automatically establish what a person’s level was while driving. Blood is usually drawn after the stop, arrest, transportation, and booking process. The prosecution may need to rely on expert testimony to relate the later test result back to the relevant driving time. That process is sometimes called retrograde extrapolation.
The time gap matters. Alcohol absorption and elimination are not identical for every person. A person’s drinking pattern, food intake, body chemistry, the time of the last drink, and the timing of the blood draw can all matter. If the sample was collected while alcohol was still being absorbed, a later result may not reliably reflect the concentration at the time of driving. This is often described as a rising blood alcohol defense, though its usefulness depends on the actual evidence, not simply the passage of time.
A DUI Blood Test Review Starts With Collection
The defense should obtain and scrutinize the records surrounding the draw, not just the final laboratory report. The arresting officer’s narrative, body-camera footage, dispatch timestamps, medical paperwork, and booking records can establish a timeline that differs from the one assumed by the prosecution.
California’s implied-consent law, Vehicle Code section 23612, governs chemical testing after a lawful DUI arrest. The law and the circumstances of the arrest can raise significant questions about whether the requested test was properly administered and whether a claimed refusal is supported. In certain situations, officers may seek a warrant for a blood draw. A warrant does not end the inquiry. Its scope, the facts offered to establish probable cause, and how the blood was ultimately taken may still require careful review.
The person performing the draw also matters. A sample must be collected by a person authorized to do so, using an appropriate procedure. Defense counsel may examine whether the skin was prepared correctly, whether the collection materials were suitable, whether the tubes were properly labeled, and whether the draw was documented accurately.
An irregularity is not automatically a dismissal. Courts generally look at whether a problem makes the result unreliable or creates a legal basis to exclude evidence. Still, a weakly documented or poorly performed collection can become important when the alleged blood-alcohol concentration is near 0.08% or when the officer’s observations are otherwise unconvincing.
The Chain of Custody Is More Than Paperwork
After the draw, the vial may pass through several hands before testing. A meaningful review follows the sample from the collection site to storage, transport, laboratory intake, analysis, and eventual retention. The prosecution must be able to establish that the vial tested was the vial drawn from the accused person and that it was not compromised along the way.
Labels, seals, evidence logs, refrigeration records, laboratory accession documents, and analyst notes can expose missing links or inconsistencies. A date or time that does not match the arrest record may be a clerical error. It may also reveal a larger problem. The point is not to assume misconduct. It is to require the government to prove the reliability of evidence it intends to use in court.
How the Laboratory Result Can Be Challenged
Blood alcohol testing commonly involves laboratory instrumentation such as gas chromatography. The final number is the product of a scientific process, not a direct observation. That process has controls, calibration requirements, maintenance records, quality-assurance procedures, and human decision-making behind it.
A focused DUI blood test review can examine whether the instrument was operating properly, whether control samples produced acceptable results, whether the analyst followed the laboratory’s procedures, and whether the result was correctly calculated and reported. Raw data, chromatograms, batch records, calibration information, and quality-control documentation may be as important as the short report provided at the outset.
Blood samples are generally collected in tubes containing additives intended to preserve the specimen and prevent clotting. Problems involving tube expiration, inadequate preservative, storage conditions, or delayed analysis can become relevant. Fermentation is sometimes raised as a defense theory, particularly where preservation or storage is questionable. It is not a catchall argument. A qualified defense expert must be able to connect the specific laboratory records and sample history to a scientifically supported concern.
Medication, medical conditions, and post-accident treatment can also require attention. For drug DUI allegations, the presence of a substance in blood does not by itself prove impairment while driving. Some medications remain detectable after their impairing effects have diminished. A prosecutor still must prove that the driver was under the influence, not merely that a test found a substance.
The Driving Evidence Still Matters
Even where there is a blood result above 0.08%, the defense should evaluate the full encounter. Why was the vehicle stopped? Was there an accident, and if so, what actually caused it? What did the body-camera video show about speech, balance, coordination, and driving? Were field sobriety tests administered under fair conditions?
For an alleged violation of section 23152(a), the issue is whether alcohol or drugs impaired driving. The officer’s conclusion is not the same thing as proof. Fatigue, anxiety, injury, uneven pavement, poor lighting, language barriers, and medical conditions can affect roadside performance and appearance.
In a near-limit alcohol case, the relationship between the driving time and draw time may be central. In a drug case, the central dispute may be impairment, the meaning of a toxicology result, or whether another cause explains the driving and observed symptoms. In other cases, an unlawful stop or unlawful arrest may support a motion to suppress evidence. The right approach depends on the records, video, witnesses, and scientific evidence available.
What Happens After a Blood Draw in Los Angeles County
A blood draw does not mean the case is over, even if an officer said the result was high. The criminal case may proceed in a Los Angeles County courthouse, while DMV consequences can involve a separate administrative process. Deadlines can be short, particularly after an arrest involving an alleged chemical-test result or refusal.
Early defense work can preserve opportunities that are harder to recover later. Counsel can request discovery, identify video and records that need preservation, assess the DMV process, review the charging allegations, and determine whether independent testing or expert consultation is warranted. Waiting until a court date approaches can mean lost footage, unavailable witnesses, and less time to analyze the sample.
Do not alter or discard prescription bottles, messages, receipts, or other potential evidence. Do not post about the arrest. If you have a medical condition, prescribed medication, or a specific recollection about your last drink, write down the facts privately for your attorney while they are fresh. Accuracy matters more than speculation.
A blood result may be strong evidence, but it must still be collected lawfully, preserved reliably, tested accurately, and placed in the correct timeline. For a confidential review of a DUI blood test or pending DUI charge in North Hollywood, Los Angeles, or anywhere in Southern California, contact Wegman & Levin APC at (818) 495-8330.
