People v. McNeal

• Decision Date: 09 July 2009
• Docket Number: No. S157565.,S157565.
• Citation: 46 Cal. 4th 1183,210 P.3d 420,96 Cal.Rptr.3d 261
• Parties: The PEOPLE, Plaintiff and Respondent, v. Timmie Lance McNEAL, Defendant and Appellant.
• Court: California Supreme Court

210 P.3d 420

96 Cal.Rptr.3d 261

46 Cal. 4th 1183

The PEOPLE, Plaintiff and Respondent, v. Timmie Lance McNEAL, Defendant and Appellant.

No. S157565.

Supreme Court of California.

July 9, 2009.

Jamie L. Popper, San Diego, and Linn Davis, Norco, for Defendant and Appellant.

Darryl W. Genis, Santa Barbara, for California DUI Lawyers Association, David Stanford, Marta Gajewski, Lyle Clayton Turner and Ronald Audia as Amici Curiae on behalf of Defendant and Appellant.

Michael A. Ramos, District Attorney, Mark A. Vos, Lead Deputy District Attorney, and Astrid G. Alfonso, Deputy District Attorney, for Plaintiff and Respondent.

Bonnie M. Dumanis, District Attorney (San Diego); Albert C. Locher, Assistant District Attorney (Sacramento); Margaret O'Malley, Deputy District Attorney (Santa Barbara); and W. Scott Thorpe, Sacramento, for California District Attorneys Association as Amicus Curiae on behalf of Plaintiff and Respondent.

CORRIGAN, J.

A defendant accused of driving under the influence of alcohol can be charged under two separate code sections. The "generic DUI" provision prohibits driving "under the influence" of alcohol. (Veh.Code, § 23152, subd. (a) (hereafter § 23152(a)).)¹ The "per se DUI" provision prohibits driving with a blood-alcohol level of 0.08 percent or more. (§ 23152, subd. (b) (hereafter § 23152(b)).) This case concerns how a generic DUI charge can be proven, or defended, at trial.

The Vehicle Code requires all drivers who are lawfully arrested for DUI to submit to chemical testing of the blood or breath to determine the alcohol content of their blood. (§ 23612, subd. (a)(1)(A).)² Whereas a blood test directly measures the subject's blood-alcohol level, a breath sample must be converted to derive a blood-alcohol percentage. The conversion factor, known as a "partition ratio," reflects the relationship between alcohol measured in a person's breath and alcohol in the blood. Breath-testing machines in California incorporate a partition ratio of 2,100 to 1, which means the amount of alcohol in 2,100 milliliters of breath is considered equivalent to the amount of alcohol in 1 milliliter of blood. It is undisputed, however, that partition ratios can vary widely, both in the general population and within an individual.

Defendant was charged with generic and per se DUI after he produced a breath sample indicating a blood-alcohol concentration of 0.10 percent. By statute, if a chemical test within three hours of driving measures a driver's blood alcohol at 0.08 percent or more, the driver is presumed to have been driving "under the influence" of alcohol. (§ 23610, subd. (a)(3) (hereafter § 23610(a)(3)).) Defendant claims he was wrongly prevented from introducing evidence about partition ratio variability to rebut this presumption. In People v. Bransford (1994) 8 Cal.4th 885, 887-888, 35 Cal.Rptr.2d 613, 884 P.2d 70 (Bransford), we confronted a similar claim in the context of the per se DUI offense. We concluded evidence about partition ratio variability is irrelevant in those cases because the Legislature incorporated a 2,100-to-1 partition ratio within its definition of the offense. (Id. at pp. 892-893, 35 Cal.Rptr.2d 613, 884 P.2d 70.)

However, a generic DUI charge is defined differently, and the presumption is not part of that definition. A generic DUI charge requires proof that the defendant's ability to drive safely was impaired because he had consumed alcohol. We conclude this difference is significant and hold that competent evidence about partition ratio variability may be admitted to defend against a generic DUI charge. Reversal is not required, though, because any error in this case was harmless under People v. Watson (1956) 46 Cal.2d 818, 836, 299 P.2d 243.

BACKGROUND

Defendant was stopped after an officer saw him drive through two red lights. Defendant's eyes were watery and bloodshot, his speech was slurred, he smelled of alcohol, and he admitted he had consumed a beer. Defendant was arrested and given a breath test about an hour after the initial stop. Defendant blew into the machine five times but produced only two samples sufficient for testing.³ Both valid samples registered a blood-alcohol level of 0.10 percent.

Defendant was charged with both generic and per se DUI.⁴ At trial, a prosecution expert testified that a person is too impaired to operate a motor vehicle safely if he displays slurred speech and bloodshot, watery eyes, commits traffic infractions, performs poorly on field sobriety tests, and records a blood-alcohol level of 0.10 percent in a breath test. A defense expert agreed that scientific authorities consider a person with a blood-alcohol level over 0.08 percent to be under the influence of alcohol. However, he considered defendant's test results unreliable because the machine's repeated failure to register sufficient samples suggested it was not functioning properly. The defense expert also testified that breath-testing machines have a margin of error of 0.02 percent.

After both sides had rested but before closing arguments, defense counsel moved to reopen to present expert testimony about partition ratio variability in connection with the generic DUI charge. The record does not disclose whether defendant intended to introduce evidence of his own partition ratio or evidence about the variability of partition ratios in the general population. The court denied the motion and instructed the jury regarding the statutory presumption of intoxication. (CALJIC No. 12.61.) Specifically, with regard to the generic DUI count, the jury was instructed: "If the evidence establishes beyond a reasonable doubt that at the time of the chemical analysis of the defendant's blood, breath or urine there was .08 percent or more, by weight, of alcohol in the defendant's blood, you may, but are not required [to,] infer that the defendant was under the influence of an alcoholic beverage at the time of the alleged offense."

The jury convicted on the generic DUI charge but hung on the per se count. Defendant moved for a new trial, arguing he should have been permitted to introduce partition ratio evidence to rebut the presumption that he was under the influence of alcohol. (§ 23610(a)(3).) Defense counsel said his expert would testify that 30 percent of the population has a partition ratio other than 2,100 to 1. When the new trial motion was denied, defendant sought relief in the superior court's appellate division, claiming the exclusion of his partition ratio evidence was reversible error. The appellate division concluded partition ratio evidence is relevant and admissible but found the error harmless given the strength of the evidence supporting the jury's verdict.

The Court of Appeal transferred the case to itself on its own motion. That court distinguished between evidence about the variability of partition ratios in the general population and evidence showing the defendant had a nonstandard ratio. It concluded evidence challenging the validity of the statutory 2,100-to-1 ratio was irrelevant, but evidence that this particular defendant had a different partition ratio should have been admitted. The court reasoned that if the defendant's own ratio differed significantly from the standard ratio, this fact could support an inference that the defendant was not actually impaired at the time of the offense. The court therefore held such personal partition ratio evidence is relevant and admissible in generic DUI cases. Although it found the defendant's offer of proof insufficient to determine the precise nature of the partition ratio evidence he sought to introduce, the Court of Appeal concluded that even assuming defendant intended to present evidence about his own ratio, and assuming the issue was preserved for review, any error was harmless under People v. Watson, supra, 46 Cal.2d at page 836, 299 P.2d 243.

The People and defendant separately petitioned for review. We granted both petitions to address the admissibility of partition ratio evidence in section 23152(a) cases.

DISCUSSION

I. The Science of Alcohol Testing

Alcohol affects the central nervous system. When ingested, it is absorbed into the blood and carried through the carotid arteries to the brain. (State v. Downie (1990) 117 N.J. 450, 569 A.2d 242, 245 (Downie); State v. Brayman (1988) 110 Wash.2d 183, 751 P.2d 294, 297 (Brayman).) After passing through the brain, alcohol travels through venous blood to the liver and heart, and from there, to the lungs, where it diffuses into alveolar air space and is exhaled in the breath. (Downie, at pp. 245-246.) As a practical matter, it is impossible to measure the amount of alcohol in a person's carotid arteries or brain. (Id. at p. 246; Taylor & Tayac, Forensic Chemist: Blood-Alcohol, supra, § 12.2, p. 712.) However, most experts agree that measurements of alcohol in venous blood or breath give a good indication of the amount of alcohol in the brain during the post-absorptive phase.⁵ (Downie, at p. 246.)

When a subject blows into a breath-testing machine, the device measures the amount of alcohol vapor expelled into alveolar spaces deep in the lungs. From this measurement of breath alcohol, a blood-alcohol percentage can be computed using a mathematical constant. The conversion from breath alcohol to blood alcohol is based on the chemistry principle of "Henry's law," which holds that there is "a constant ratio between the concentration of alcohol in the blood and the concentration of alcohol in the alveolar air of the lungs." (Taylor & Tayac, Forensic Chemist: Blood-Alcohol, supra, § 12.19, p. 770.) Breath-testing machines in California use a conversion factor of 2,100 to 1, meaning "the amount of alcohol in 2,100 milliliters of alveolar breath is equivalent to the amount of alcohol in 1 milliliter of blood." (Cal.Code Regs., tit. 17, § 1220.4, subd. (f); see People v. McDonald (1988) 206 Cal.App.3d 877, 880, 254 Cal.Rptr. 384.) This ratio is used, apparently without...