A different number on the roadside test and the station test does not by itself mean either reading is wrong. The two tests are given at different times and play different legal roles in a DUI case, and when a breath test reports an alcohol concentration, roadside or at the station, California’s Title 17 testing regulations apply to it. The gap is a reason to examine how each test was actually given.

Two tests, two roles

The handheld test an officer offers at the roadside is a preliminary alcohol screening (PAS) test. A PAS test that indicates the presence or concentration of alcohol from a breath sample, given to establish reasonable cause to believe the person was driving in violation of Vehicle Code section 23140, 23152, or 23153, is by statute a field sobriety test that an officer may use as a further investigative tool (Vehicle Code section 23612(h)). Taking the PAS test does not satisfy your separate duty to submit to a blood, breath, or urine test after a lawful arrest, and the officer must tell you that you have the right to refuse the PAS test itself (Vehicle Code section 23612(i)). The breathalyzer test given later at the station is the chemical test administered after arrest.

Title 17 applies to both kinds of test, but noncompliance does not automatically exclude a result

Title 17 of the California Code of Regulations sets the procedures for breath alcohol testing: two separate breath samples whose results do not differ from each other by more than 0.02 grams per 210 liters of breath, accuracy checks at least every 10 days or after every 150 subjects tested, whichever comes sooner, and a sample collected only after 15 continuous minutes in which the person has not eaten, drunk, smoked, vomited, or regurgitated (17 CCR 1221.2; 17 CCR 1221.1). In a footnote, the California Supreme Court agreed with the Court of Appeal’s explanation in People v. Bury that the Title 17 regulations apply to a PAS test that determines the concentration of alcohol, though not to one that shows only whether alcohol is present, and said Bury properly rejected as dicta an earlier finding, in Coniglio v. Department of Motor Vehicles, that Title 17 never applies to PAS tests (People v. Williams (2002) 28 Cal.4th 408, fn. 2).

The California Highway Patrol’s own policy manual takes a different position for its own purposes, stating that “Title 17 does not apply to PAS devices,” while modeling its PAS policy on Title 17 anyway “to increase the weight of the PAS device evidence in court” (CHP Highway Patrol Manual 70.4, chapter 7). That is the department’s internal policy, not the rule the Supreme Court described in Williams.

Either way, a failure to follow Title 17 does not automatically throw a result out. Williams held that breath test results are admissible on a showing of Title 17 compliance, or on a separate showing that the equipment was working properly, the test was properly administered, and the operator was qualified; noncompliance goes to the weight of the evidence, not its admissibility. Without either showing, the result is not admissible. When there is evidence the regulations were not followed, CALCRIM No. 2111 (2026 edition) tells jurors that in evaluating “any test results in this case” they may consider whether the person giving the test or the agency maintaining the device followed the California Department of Public Health’s regulations.

Which number matters

Vehicle Code section 23152(b) makes it, in a prosecution under that subdivision, a rebuttable presumption that a person had 0.08 percent or more at the time of driving if the person had 0.08 percent or more “at the time of the performance of a chemical test within three hours after the driving.” CALCRIM No. 2111 presents this to jurors as a permissive inference: if the People prove beyond a reasonable doubt that a breath or blood sample taken within three hours showed 0.08 percent or more, the jury may, but is not required to, conclude the level was 0.08 percent or more when the person drove. Neither the statute nor the instruction says which test, roadside or station, counts. The roadside number is not automatically beside the point: in Williams, where the driver refused the chemical test after arrest, a roadside PAS reading was admitted on a charge of driving under the influence, and the Supreme Court upheld its admission as evidence that tended to establish intoxication.

What to check

  • The make and model of both the PAS device and the station instrument, and each one’s calibration and accuracy-check records.
  • Whether the station’s two samples actually agreed within 0.02 grams per 210 liters, and what the raw numbers were.
  • Whether the 15-minute period before each test is documented, and by whom.
  • The time of the roadside test, the time of the station test, and everything that happened in between.

When refusing the roadside test has license consequences

Two situations attach license consequences to the PAS test. If you are under 21 and an officer who lawfully detains you has reasonable cause to believe you are violating the zero-tolerance law (Vehicle Code section 23136), the officer must request a PAS test if a device is immediately available, and otherwise may request a chemical test; refusing or failing to complete the test, or a result of 0.01 percent or more, requires the officer to serve a notice of an order suspending your driving privilege (Vehicle Code section 13388). If you are on probation for a DUI conviction under section 23152 or 23153, it is separately unlawful to drive with 0.01 percent or more as measured by a PAS or other chemical test (Vehicle Code section 23154); on reasonable cause, the officer must request a PAS test if one is immediately available, and a refusal, a failure to complete it, or a PAS result of 0.01 percent or more requires the officer to serve a notice of suspension (Vehicle Code section 13389). In either situation, refusing or failing to complete the PAS test leads to a one-year suspension, or a two- or three-year revocation depending on your record in the prior 10 years (Vehicle Code section 13353.1).

If the station test did not follow Title 17’s procedures, that is a distinct challenge covered on the firm’s Title 17 violations page. If a later test was refused instead of taken, that raises separate issues on the firm’s refusal cases page. And if the gap between tests reflects your body still absorbing alcohol, see the firm’s rising blood alcohol defense page.

Your specific test records are worth a closer look: reach the Law Offices of David S. Chesley at (800) 755-5174.