The absence of a retained sample for retesting does not automatically exclude the official DUI blood result. The next questions are why no test can be done, which testing right applied, what records remain, and whether the circumstances support a specific legal challenge.
Two provisions address different things. Vehicle Code section 23158(b) permits a person to obtain an additional test at their own expense and expressly says that failure or inability to obtain that additional test does not itself prevent admission of the officer-directed test. Subdivision (c) requires information about the test on request. This is not a guarantee of a free half-sample or automatic access to one. Vehicle Code § 23158.
Separately, Title 17, California Code of Regulations, section 1219.1(f) addresses retention and access to a remaining forensic-alcohol sample. The current text generally requires retention for one year for defendant analysis, subject to a 90-day coroner or medical-examiner exception; if a sufficient sample remains when requested, a portion and identifying information are provided. Whether this regulation applies depends on the type of forensic-alcohol sample and who held it. Counsel should check the governing circumstances before applying its timing rule. 17 CCR § 1219.1.
First identify why the sample is unavailable
“Unavailable” can describe different events: no sample was drawn; the original was consumed during testing; too little remained; the sample degraded; or it was lost or destroyed. Each presents a different factual question. If no specimen was collected, there may be no retained-sample request to make. If testing consumed it or left too little, the volume and test records matter. If it degraded, storage conditions and timing may be relevant. If it was lost or destroyed, the chain of custody, retention rule, notice, and reason for disposition become important. Counsel may seek the collection and analysis records, original test information, volume records, storage conditions, transfer logs, retention and destruction dates, and communications about requests for testing. The lab’s raw data and method records may also provide material to review even if the physical sample is gone.
The record may show whether the sample was ever suitable for a second analysis, when it became unavailable, and what officials knew at that time. Do not assume the sample was destroyed improperly simply because it cannot now be retested; likewise, an explanation should be evaluated against the applicable procedure and records.
A preservation claim requires its own analysis
Federal due-process decisions distinguish evidence whose exculpatory value was apparent before destruction, when comparable evidence was not reasonably available, from evidence that was only potentially useful. California v. Trombetta addressed breath samples and does not create an automatic remedy for every missing blood sample. For evidence that is only potentially useful, Arizona v. Youngblood and Illinois v. Fisher require a showing of bad faith for a federal due-process violation. Trombetta; Youngblood; Fisher.
Whether a preservation issue supports relief depends on what the sample could show, the reason and timing of its unavailability, applicable retention rules, and the remaining evidence. Missing a retest opportunity does not promise suppression, dismissal, or any particular inference. The Law Offices of David S. Chesley DUI blood-test page explains related testing issues. For case-specific review, call (800) 755-5174.