The “3 Hour Rule”

The 3 hour presumption is a rule that requires a chemical test be performed within 3 hours of the time of driving.  The rule originates in VC23152b and essentially gives the prosecution the benefit of proving the person had the same blood alcohol level at the time of driving.  The rule is rebuttable, meaning if any evidence is presented to show the person did not have the same BAC then the ”presumption “ disappears.

In California It is axiomatic that the Department bears the burden of proving the facts necessary to support the suspension of a driver’s license. Daniels v. Department of Motor Vehicles, (1983) 33 Cal. 3d 532, 536, 189 Cal. Rptr. 512, 658 P. 2d 1313 (“The burden of proving facts necessary to support a suspension of a license rests with DMV. Until DMV has met its burden of producing

competent evidence necessary to establish a prima facie case, the licensee has no duty to rebut the allegations or otherwise respond.” [Italics in original]), and that one of the elements which must be proven by the Department is that the licensee’s BAC was .08 or higher at the time of driving. Yordamlis v. Department of Motor Vehicles, (1992) 11 Cal. App. 4th 655, 661 (FN 5), 14 Cal. Rptr. 2d 225 (“…suspension under section 13353.2 depends on proof of a BAC at the time of driving, not on proof that the driver was under the influence.” [Emphasis added.]).  

The Santos Court enunciated that the absence of evidence of a start or end time, negates application of the three hour presumption, stating:

“The Department did not rebut respondent’s evidence that the test results failed to prove her blood alcohol level at the time of driving was 0.08 percent or higher and, in fact, that her blood alcohol level at the time of driving was less than 0.08 percent. Whether or not the trial court accepted this evidence to the point of believing respondent’s blood alcohol was in fact lower than 0.08 percent at the time of driving, it is obvious that the laboratory test results failed to provide a piece of information critical to a determination of the level of alcohol in respondent’s blood at the time of driving. While the absence of evidence of the time respondent’s blood sample was taken did not render the test result inadmissible, without such evidence the Department simply could not meet its burden of proof. The hearing officer was permitted to draw inferences and deductions from the facts before him or her (Evid. Code, §600, subd. (b)); given the complete absence of evidence as to when respondent’s blood sample was drawn, however, there was no basis for an inference that respondent’s blood alcohol level was 0.08 percent or more at the time of driving”[Emphasis added.]

Santos v. Department of Motor Vehicles, (1992) 5 Cal. App. 4th 537, 549-550, 7 Cal. Rptr. 2d 10;

see also Yordamlis at 661 (“…there is no evidence that Yordamlis gave the tested blood sample within three hours of driving. Therefore, the “3 hour presumption” does not apply.”

The “3 Hour Presumption “ is particularly useful in accident cases where no driving was observed.  If the time of the collision is not determined, the blood or breath results may be excluded.

Indeed, California EVID. CODE §600 sets forth: “a presumption may not be applied unless the necessary facts justifying application of the presumption have been established.  The prosecution bears the burden of proving the accused’s driving time in order to justify application of the three-hour presumption.

The law is clear—the Prosecution, whether it be the District Attorney in a criminal case or the Department of Motor Vehicles in a DMV Hearing,  bears the burden of proving the Licensee’s BAC was .08 or more at the time of driving, and the evidence that is critical to the Department’s burden of proof—the time the Licensee actually drove his car—has not been established.

It is indisputable  that the official duty presumption does not apply when determining if the test was administered to determine a licensee’s BAC was administered within three hours of driving.  The law in this regard is unequivocal—presumptions are not evidence and may be utilized only when justified by facts proven by the evidence.

Top Tier DUI Attorney Matthew Ruff has over 30 years experience fighting and winning drunk driving cases using the 3 hour presumption and many other defenses.

If you are facing a California DMV administrative hearing for a driving under the influence (DUI) arrest, one of the most critical elements the state must prove is your Blood Alcohol Concentration (BAC) at the exact time of driving. However, chemical tests are inevitably taken after a stop or collision occurs.  

To bridge this gap, California law utilizes a legal shortcut known as the 3-Hour Presumption. But what happens when the state cannot prove exactly when you were driving? The answer is simple: the presumption disappears, and the DMV's case can completely fall apart.  

What is the 3-Hour Presumption?

Under California Vehicle Code § 23152(b), there is a rebuttable presumption that a driver had a BAC of 0.08% or higher at the time of driving if a chemical test shows a BAC of 0.08% or higher, and that test was performed within three hours of driving.
If the DMV cannot establish a definitive "start time"—the precise timeframe when the vehicle was in motion—they cannot legally calculate the three-hour window. Without this foundation, the 3-hour presumption cannot be applied.  

The Legal Burden on the DMV

In an Administrative Per Se (APS) hearing, the Department of Motor Vehicles holds the absolute burden of proving the facts necessary to support a license suspension. As established in foundational California case law:  

Daniels v. DMV (1983): The burden of producing competent evidence rests solely with the DMV. Until they meet a prima facie case, the licensee has no legal duty to rebut allegations.  

Yordamlis v. DMV (1992): Suspension depends on proof of an illegal BAC at the time of driving, not simply proof that the driver was under the influence at some point.  

Santos v. DMV (1992): No presumption can supply missing information when an official report fails to indicate the necessary times. Without a proven time of driving or sample collection, there is no basis for an inference of an illegal BAC while behind the wheel.  

If the 3-hour presumption is blocked, the DMV must provide alternative, sophisticated evidence—such as a toxicologist performing retrograde extrapolation—to prove what the driver's BAC was hours earlier (McKinney v. DMV, 1992). If they fail to provide this expert testimony, a Set Aside of the suspension is legally compelled under Vehicle Code § 14105(a).  

Case Victory: How Lack of "Time of Driving" Saved a License

A real-world example handled by The Law Offices of Matthew Ruff highlights exactly how powerful this defense can be when aggressively argued at a DMV Administrative Hearing.  

The Incident & Arrest

A driver was contacted by the California Highway Patrol (CHP) at approximately 2:30 AM following a traffic crash investigation on eastbound I-105. Based on objective symptoms of intoxication and poor performance on Field Sobriety Tests (FSTs), the officer placed the driver under arrest at 3:42 AM. Preliminary Alcohol Screening (PAS) tests yielded results of 0.135% and 0.124%, and subsequent evidential breath tests taken at 4:27 AM registered a BAC of 0.12%.  

The Fatal Flaw in the DMV's Case

While the officer documented the time of the contact (2:30 AM) and the arrest (3:42 AM), the officer failed to establish the actual time of driving on the official DS 367 Officer's Statement.  

Because the vehicle was already stopped when law enforcement arrived at the crash scene, and no competent evidence established exactly how long the vehicle had been stationary prior to 2:30 AM, there was no valid "start time".  

The Outcome: Complete Set Aside

Attorney Matthew Ruff submitted a comprehensive Administrative Hearing Brief arguing that because the time of driving was unknown, the 3-hour presumption was entirely inapplicable. Because the DMV could not legally bridge the 4:27 AM breath test results back to an unproven time of driving, they failed their foundational burden of proof.  

The DMV Driver Safety Branch reviewed the merits of the defense and issued an official Order of Set Aside. The suspension of the client's driving privilege was completely overturned, allowing them to legally retain their California driver's license.  

Facing a California DMV Hearing?

DMV administrative hearings are highly technical and governed by strict evidentiary rules. If an officer cuts corners or fails to properly document the timeline of your arrest, it could mean the difference between a multi-month suspension and keeping your license.