Filed 4/6/15

IN THE SUPREME COURT OF CALIFORNIA

ASHLEY JOURDAN COFFEY, )

)

Plaintiff and Appellant, )

) S213545

v. )

) Ct.App. 4/3 G047562

JEAN SHIOMOTO, as Director, etc., )

) Orange County

Defendant and Respondent. ) Super. Ct. No. 30-2012-00549559

____________________________________)

A California Highway Patrol officer stopped a car driven by plaintiff 

Ashley Jourdan Coffey after he observed her driving erratically. Four subsequent 

chemical tests revealed her blood-alcohol concentration (BAC) ranged from 0.08 

to 0.096 percent. The officer then confiscated plaintiff‘s driver‘s license and 

served her with a notice that her license would be suspended pursuant to Vehicle 

Code section 13382.1 In an administrative hearing to review the suspension, 

plaintiff‘s expert witness opined that her BAC was rising at the time of the 

chemical tests, suggesting her BAC was below the 0.08 percent threshold at the 

time plaintiff was driving. Both the Department of Motor Vehicles (DMV) 

hearing officer and the trial court discounted the expert‘s testimony in part by 

relying on arrest reports, which described the physical manifestations of plaintiff‘s 

 

1 All statutory references are to the Vehicle Code unless otherwise stated.
2

intoxication, such as her general appearance, erratic driving, poor performance on 

field sobriety tests, and the strong odor of alcohol she projected. 

We decide in this case whether the trial court erred by considering, in 

addition to the results of breath and blood tests, other circumstantial evidence of 

intoxication to conclude by a preponderance of the evidence that plaintiff drove 

with a BAC at or above 0.08 percent. As we explain, we conclude the trial court 

did not err.

FACTS

On November 13, 2011, at 1:32 in the morning, Sergeant Martin of the 

California Highway Patrol was traveling southbound on State Route 55 in Orange 

County when he saw a car traveling 60 miles per hour, swerving erratically from 

side to side. From the number four, or right-hand, lane, the car swerved one foot 

to the left into the number three lane before correcting. It then twice swerved one 

to two feet to the right, onto the highway‘s shoulder. Sergeant Martin positioned 

his patrol vehicle behind the car and activated his emergency lights, whereupon 

the car slowly moved left across the highway into the number one lane. When 

Martin activated his siren, the car veered even further left, into the carpool lane. 

Only when Sergeant Martin used his public address system and directed the driver 

to pull to the right did the car eventually comply. 

Upon making contact with the driver of the vehicle, plaintiff Ashley 

Coffey, Sergeant Martin noticed her eyes were red and a strong odor of alcohol 

emanated from her car. Officer White arrived to provide backup and confirmed 

these observations. To both officers she denied having consumed any alcoholic 

beverages, offering the rather implausible story that she had just turned 21 years 

old, had been in a bar, but had not herself consumed any alcoholic beverages. The 

officers then had plaintiff perform various field sobriety tests. Plaintiff failed the 

horizontal gaze nystagmus test, ―display[ing] a lack of smooth pursuit in both 
3

eyes.‖

2 Asked to complete the ―walk-and-turn test,‖ in which she was asked to 

walk heel to toe for nine steps, turn counterclockwise, and then walk back heel to 

toe, ―she missed heel to toe on five of those nine steps by 2–4 inches on each step. 

When she reached step nine, . . . she turned clockwise instead of counter clockwise 

as instructed. . . . [She] used both feet to make the turn instead of keeping her 

front foot in place‖ and on the return similarly ―missed heel to toe three of the 

steps by 2–4 inches.‖3 

 

2 ―  ̳Nystagmus is an involuntary rapid movement of the eyeball, which may 

be horizontal, vertical, or rotary. [Citation.] An inability of the eyes to maintain 

visual fixation as they are turned from side to side (in other words, jerking or 

bouncing) is known as horizontal gaze nystagmus, or HGN. [Citation.] Some 

investigators believe alcohol intoxication increases the frequency and amplitude of 

HGN and causes HGN to occur at a smaller angle of deviation from the forward 

direction.‘ ‖ (People v. Leahy (1994) 8 Cal.4th 587, 592.)

3 The ―  ̳walk-and-turn test‘ ‖ is significant because it tests ―  ̳many of the 

same skills needed for driving,‘ such as small muscle control, information 

processing, reaction, balance, coordination, and short-term memory.‖ (U.S. v. 

Stanton (9th Cir. 2007) 501 F.3d 1093, 1100.) 

―Officers administering the Walk-and-Turn test observe the suspect‘s 

performance for eight clues:

―• can‘t balance during instructions;

―• starts too soon;

―• stops while walking;

―• doesn‘t touch heel-to-toe;

―• steps off line;

―• uses arms to balance;

―• loses balance on turn or turns incorrectly; and,

―• takes the wrong number of steps.‖ 

(Utah Prosecution Council, Driving Under the Influence Prosecution Manual 

(2007) ch. 8, p. 8 <http://www.justice.state.ut.us/Documents/Sentencing/

ProsecutionManual/chapter 8.pdf> [as of April 6, 2015] (Utah Prosecution 

Manual).) ―Original research shows that if a suspect exhibits two or more of the 

clues, or cannot complete the test, the suspect‘s BAC is likely to be above 0.10

[percent]. This criterion has been shown to be accurate 68 percent of the time.‖ 

(Ibid.)
4

Plaintiff did somewhat better on the ―one-leg stand‖ test,4 standing on one 

foot and counting out loud beginning with 1,001; the test was terminated when she 

reached 1,022 after 30 seconds. On the Romberg test,5 ―[s]he swayed slightly in 

 

4 In the ―one-leg stand‖ test, after listening to the instructions, ―the subject 

must raise one leg, either leg, with the foot approximately six inches off the 

ground, keeping raised foot parallel to the ground. While looking at the elevated 

foot, count out loud in the following manner:

―  ̳[O]ne thousand and one‘,  ̳one thousand and two‘,  ̳one thousand and

three‘ until told to stop. This divides the subject‘s attention between balancing 

(standing on one foot) and small muscle control (counting out loud).

―The timing for a thirty-second period by the officer is an important part of

the One-Leg Stand test. The original research has shown that many impaired 

subjects are able to stand on one leg for up to 25 seconds, but that few can do so 

for 30 seconds.

―One-Leg Stand is also administered and interpreted in a standardized

manner. Officers carefully observe the suspect‘s performance and look for

four specific clues:

―• sways while balancing;

―• uses arms to balance;

―• hops;

―• puts foot down.

―Inability to complete the One-Leg Stand test occurs when the suspect:

―• puts the foot down three or more times, during the 30-second period;

―• cannot do the test.

―The original research shows that, when the suspect produces two or more

clues or is unable to complete the test, it is likely that the BAC is above 0.10

[percent]. This criterion has been shown to be accurate 65 percent of the time.‖ 

(Utah Prosecution Manual, supra, ch. 8, at pp. 8–9 <http://www.justice.state.ut.us/

Documents/Sentencing/ProsecutionManual/chapter8.pdf> [as of April 6, 2015].)

5 In the Romberg test, the driver is ―asked to stand at attention, close his 

eyes, tilt his head back, and estimate the passage of 30 seconds.‖ (People v. 

Bejasa (2012) 205 Cal.App.4th 26, 33.) The officer observes the driver‘s ―balance 

and his ability to accurately measure the passage of 30 seconds.‖ (Ibid.)
5

all directions from center by 1–2 inches‖ and ―estimated 30 seconds at 37 actual 

seconds.‖ Plaintiff refused to perform a preliminary alcohol screening, or PAS.

6

Based on the officers‘ observations of plaintiff and her poor performance 

on the field sobriety tests, they placed her under arrest at 2:00 a.m. Officer White 

advised her of the implied consent law7 and she chose to perform a breath test, 

although she failed several times to provide an adequate breath sample and had to 

be retested multiple times. At 2:28 a.m., 56 minutes after she was stopped by 

Sergeant Martin, her breath test registered a BAC of 0.08 percent. Three minutes 

later, at 2:31 a.m., her second breath test measured a BAC of 0.09 percent. Police 

then transported plaintiff to the Orange County jail, where she elected to have her 

blood drawn. The blood draw occurred at 2:55 a.m., one hour 23 minutes after 

plaintiff was pulled over by Sergeant Martin. The first test of the blood sample

showed a BAC of 0.095 percent; the second measured 0.096 percent. As a result 

of these chemical test results, Officer White confiscated plaintiff‘s driver‘s license 

 

6 Pursuant to section 23612, subdivision (h), a PAS is an investigative tool 

used to determine whether there is reasonable cause for arrest. ―[A] preliminary 

test is  ̳distinguished from the chemical testing of a driver‘s blood, breath or urine 

contemplated by the implied consent law [citation] which is administered after the 

driver is arrested, [and is] sometimes referred to as ―evidentiary‖ [or evidential] 

testing.‘ ‖ (People v. Vangelder (2013) 58 Cal.4th 1, 5, fn. 1.)

7 ―A person who drives a motor vehicle is deemed to have given his or her 

consent to chemical testing of his or her blood or breath for the purpose of 

determining the alcoholic content of his or her blood, if lawfully arrested for an 

offense allegedly committed in violation of Section 23140, 23152, or 23153.‖ 

(§ 23612, subd. (a)(1)(A).) ―The person shall be told that his or her failure to 

submit to, or the failure to complete, the required chemical testing will result in a 

fine, mandatory imprisonment if the person is convicted of a violation of Section 

23152 or 23153, and . . . suspension or revocation of the person‘s privilege to 

operate a motor vehicle . . . .‖ (§ 23612, subd. (a)(1)(D).)
6

and issued her an ―administrative per se suspension/revocation order‖ and 

temporary driver‘s license. (§ 13382; see Lake v. Reed (1997) 16 Cal.4th 448, 

454–455 (Lake).)

Plaintiff, charged with drunk driving (§ 23152), was allowed to plead to a 

―wet reckless‖ (§§ 23103 [misdemeanor reckless driving], 23103.5 [prosecutorial 

statement that alcohol was involved]; see People v. Claire (1991) 229 Cal.App.3d 

647, 650 & fn. 2), but requested a hearing before the DMV to challenge her 

license suspension (§ 13558). 

At the ensuing administrative hearing, the DMV hearing officer had before 

her the ―Officer‘s Sworn Statement‖ form, Officer White‘s arrest report and the 

supplemental reports of Sergeant Martin and Officer White. In addition to 

considering these documents, the hearing officer heard telephonic testimony from 

Jay Williams, a forensic toxicologist with extensive experience, who testified for 

plaintiff. Williams noted the result of plaintiff‘s first breath test was 0.08 percent, 

the second test three minutes later was 0.09 percent, and her blood sample taken

about 20 minutes later tested at 0.095 and 0.096 percent. According to Williams, 

these results suggested the alcohol level in plaintiff‘s body was rising at the time 

of the tests and, given the totality of the circumstances, were consistent with 

plaintiff‘s BAC being below 0.08 percent at 1:32 a.m. when she was first pulled 

over by Sergeant Martin.

The DMV hearing officer rejected Williams‘s testimony regarding a rising 

BAC, explaining in her ruling that the witness‘s two conclusions—first, that 

plaintiff‘s BAC was rising at the time she was pulled over, and second, that it may 

accordingly be deduced that her BAC was below 0.08 percent when she was 

driving—were not supported by reliable evidence, were ―too speculative to 

support the contention,‖ and were ―based on a subjective interpretation of the 

evidence.‖ In addition, Williams‘s conclusions were ―insufficient to rebut the 
7

official duty presumption,‖ which in this context we take to be a reference to the 

presumption the chemical test results were valid.8 The hearing officer reached this 

conclusion, she explained, because Williams had not himself examined the breathanalyzing device used in the case, offered no opinion whether it was in working 

order, conducted no scientific tests himself, and ―did not show that any other 

experts in the scientific community had reached similar conclusions.‖ Finally, the 

hearing officer specifically found credible Officer White‘s recordation of the 

―events as they occur[red],‖ which we assume meant White‘s observations of 

plaintiff‘s appearance and her performance on field sobriety tests. Accordingly, 

the hearing officer concluded plaintiff‘s license suspension was proper because the 

state had shown by a preponderance of the evidence that she had been driving with 

a BAC of 0.08 percent or higher. 

Plaintiff filed a petition for a writ of mandate with the trial court to 

challenge the DMV hearing officer‘s decision. After first noting that section 

23152, subdivision (b) makes it a rebuttable presumption that a person was driving 

with a BAC of 0.08 percent or higher if so tested at that level or higher within 

three hours of driving (see discussion, post), the trial court denied the writ, 

 

8 Evidence Code section 664 provides in part: ―It is presumed that official 

duty has been regularly performed.‖ Applied in this context, ―Evidence Code 

section 664 creates a rebuttable presumption that blood-alcohol test results 

recorded on official forms were obtained by following the regulations and 

guidelines of [Cal. Code Regs.] title 17. [Citations.] Test results from authorized 

laboratories, performed by public employees within the scope of their duties, are 

admissible under the public employee records exception to the hearsay rule. 

[Citations.] The recorded test results are presumptively valid and the DMV is not 

required to present additional foundational evidence. [Citation.] At this point, 

 ̳faced with a report of chemical test results, the burden would be on the licensee to 

demonstrate that the test was not properly performed.‘ ‖ (Shannon v. Gourley

(2002) 103 Cal.App.4th 60, 64–65.)
8

explaining that ―[e]ven assuming that petitioner Coffey rebutted [this] 

presumption . . . , there was sufficient evidence based on the blood-alcohol tests 

and the other circumstantial evidence based on the assessment, observations and 

tests by the arresting officers at the scene to support the DMV hearing officer‘s 

decision under the weight of the evidence.‖ (Italics added.) 

The Court of Appeal affirmed. In determining whether the trial court‘s 

decision was supported by substantial evidence, the appellate court opined that 

―[t]he issue boils down to whether non-chemical-test circumstantial evidence can 

prove that Coffey‘s BAC at the time of driving was consistent with her BAC at the 

time of her chemical tests.‖ Relying on this court‘s opinion in Burg v. Municipal 

Court (1983) 35 Cal.3d 257, the appellate court held in the affirmative. We 

granted review.

DISCUSSION

A. Background

The DMV suspended plaintiff‘s license to drive pursuant to the 

―administrative per se‖ law, ―under which a person arrested for driving under the 

influence of alcohol, and who is determined to have a prohibited amount of 

alcohol in his or her blood, must have driving privileges suspended prior to an 

actual conviction for a criminal offense.‖ (Lake, supra, 16 Cal.4th at p. 454.) As 

we explained in that case, ―  ̳[t]he express legislative purposes of the 

administrative suspension procedure are: (1) to provide safety to persons using the 

highways by quickly suspending the driving privilege of persons who drive with 

excessive blood-alcohol levels; (2) to guard against erroneous deprivation by 

providing a prompt administrative review of the suspension; and (3) to place no 

restriction on the ability of a prosecutor to pursue related criminal actions.‘ ‖

(Ibid.) ―[T]he administrative per se laws were deemed necessary due to the time 
9

lag that often occurs between an arrest and a conviction for driving while 

intoxicated or with a prohibited BAC. During this interim period, arrestees who 

could eventually be convicted of an intoxication-related driving offense were 

permitted to continue driving and, possibly, endangering the public thereby. 

Moreover, without administrative per se laws, persons with extremely high BAC 

levels at the time of arrest could escape license suspension or revocation by plea 

bargaining to lesser crimes or entering pretrial diversion. Thus, by providing for 

an administrative license suspension prior to the criminal proceeding, the law 

affords the public added protection.‖ (Id. at pp. 454–455.)

Pursuant to the administrative per se law, ―[a]fter either the arresting officer 

or the DMV serves a person with a  ̳notice of an order of suspension or revocation 

of the person‘s [driver‘s license],‘ the DMV automatically reviews the merits of 

the suspension or revocation. [Citation.] The standard of review is preponderance 

of the evidence [citation], and the department bears the burden of proof.‖ (Lake, 

supra, 16 Cal.4th at p. 455.) A driver served with such a suspension notice is 

entitled to a hearing on request (§ 13558, subd. (a)), at which the only issues to be 

decided for drivers such as plaintiff9 are whether the arresting officer had 

reasonable cause to believe she was driving, whether she was arrested for an 

enumerated offense, and whether she was driving with 0.08 percent BAC or 

higher. (§ 13557, subd. (b)(3)(A), (B), & (C)(i).) If the DMV hearing officer 

finds these three statutory prerequisites proved by a preponderance of the 

evidence, the accused‘s driver‘s license will be suspended for four months if the 

 

9 Somewhat different rules apply to those under 21 years of age (§ 13557, 

subd. (b)(3)(C)(ii)), those driving commercial vehicles (id., subd. (b)(3)(C)(iv)), 

and those on probation for prior drunk driving convictions (id., subd.

(b)(3)(C)(v)).
10

driver has had a clean driving record (§ 13353.3, subd. (b)(1)). Higher penalties 

apply to those with prior drunk driving convictions. (§ 13353.3, subd. (b)(2).) 

B. The Rebuttable Presumption in Section 23152

We first address whether the presumption created by section 23152, 

subdivision (b) controls this case. That provision states in part: ―In any 

prosecution under this subdivision, it is a rebuttable presumption that the person 

had 0.08 percent or more, by weight, of alcohol in his or her blood at the time of 

driving the vehicle if the person had 0.08 percent or more, by weight, of alcohol in 

his or her blood at the time of the performance of a chemical test within three 

hours after the driving.‖ Although the statutory language speaks in terms of a 

―prosecution,‖ several Courts of Appeal have held this presumption is not limited 

to criminal prosecutions but also applies in administrative license suspension 

proceedings. (Corrigan v. Zolin (1996) 47 Cal.App.4th 230, 236, citing Jackson v. 

Department of Motor Vehicles (1994) 22 Cal.App.4th 730, 740, fn. 9, and Bell v. 

Department of Motor Vehicles (1992) 11 Cal.App.4th 304, 310–313.) 

Extending the reach of Vehicle Code section 23152, subdivision (b)‘s 

evidentiary presumption to administrative per se proceedings would be consistent 

with the legislative history of that provision. The need for the presumption ―arose 

from the absence in  ̳[e]xisting law‘ of any  ̳provision for the delay involved 

between the time a person is arrested for [driving under the influence] and when 

the chemical test for BAC is actually administered,‘ of any  ̳means to determine a 

person‘s BAC at the time the person is actually driving the car,‘ or of any 

 ̳mention of time parameters for the administering of chemical tests and for their 

admission as [admissible] evidence into a court of law.‘ (Health & Welf. Agency, 

Dept. of Alcohol & Drug Programs, Enrolled Bill Rep. for Sen. Bill No. 745 

(1981–1982 Reg. Sess.) Sept. 1982, original italics.) Thus, in enacting the 
11

presumption, the Legislature intended (1) to  ̳diminish the arguments that ha[d] 

arisen when extrapolating the [BAC] at the time of the test back to the time of the 

driving‘ (Bus. & Transportation Agency, DMV, Enrolled Bill Rep. for Sen. Bill 

No. 745 (1981–1982 Reg. Sess.) Sept. 1982), (2)  ̳to close a potential loophole in 

the current law, whereby a person . . . could claim that he or she had consumed . . . 

alcohol which had not yet been absorbed into the bloodstream while the person 

was operating the vehicle, but which later raised the blood alcohol level‘

(Governor‘s Office, Dept. of Legal Affairs, Enrolled Bill Rep. for Sen. Bill No. 

745 (1981–1982 Reg. Sess.) Sept. 1982), and (3)  ̳to recognize that alcohol 

concentrations dissipate over time, so that a person whose blood alcohol levels 

exceed the permissible concentrations at the time of the test, was likely to have 

had unlawfully high blood alcohol levels when driving . . . .‘ ‖ (Bell v. 

Department of Motor Vehicles, supra, 11 Cal.App.4th at p. 311.) These three 

statements of legislative intent would arguably apply to administrative per se 

proceedings as well.

Consistent with the previously cited Court of Appeal cases, both parties 

assume section 23152‘s presumption applies in administrative per se hearings. We 

need not resolve that question, however, because even were the presumption 

applicable, it was rebutted in this case. An explanation of how the presumption 

operates can be found in the Evidence Code. Section 601 of that code provides: 

―A presumption is either conclusive or rebuttable. Every rebuttable presumption 

is either (a) a presumption affecting the burden of producing evidence or (b) a 

presumption affecting the burden of proof.‖ Vehicle Code section 23152, 

subdivision (b), by its terms, creates a rebuttable presumption, and we agree with 

the parties that it establishes a presumption affecting the burden of producing 

evidence, not the burden of proof. A statute transferring the burden of proof to a 

driver facing a criminal charge of drunk driving would raise serious constitutional 
12

questions (see Ulster County Court v. Allen (1979) 442 U.S. 140, 157 [a 

permissive presumption is constitutional if, among other things, it ―does not shift 

the burden of proof‖]; see People v. Gamache (2010) 48 Cal.4th 347, 376 

[rejecting claim that jury instruction ―impermissibly alters the burden of proof,‖ 

explaining the ―instruction does not establish an unconstitutional mandatory 

presumption in favor of guilt [citation] or otherwise shift or lower the 

prosecution‘s burden of establishing guilt beyond a reasonable doubt‖]), and 

although those concerns are inapplicable here because it is an administrative per se 

proceeding, neither party argues for a different construction. (See People v. 

Dubon (2001) 90 Cal.App.4th 944, 953 [―When a presumption is established to 

facilitate the determination of the particular action in which the presumption is 

applied, rather than to implement public policy, it is a presumption affecting the 

burden of producing evidence.‖].)

A rebuttable presumption requires the trier of fact, given a showing of the 

preliminary fact (here, that a chemical test result showed plaintiff had a BAC of 

0.08 percent or more within three hours of driving), to assume the existence of the 

presumed fact (here, that plaintiff had been driving with a prohibited BAC)

―unless and until evidence is introduced which would support a finding of its 

nonexistence, in which case the trier of fact shall determine the existence or 

nonexistence of the presumed fact from the evidence and without regard to the 

presumption.‖ (Evid. Code, § 604.) In other words, if evidence sufficient to 

negate the presumed fact is presented, the ―presumption disappears‖ (Craig v. 

Brown & Root, Inc. (2000) 84 Cal.App.4th 416, 421) and ―has no further effect‖ 

(In re Heather B. (1992) 9 Cal.App.4th 535, 561), although ―inferences may 

nevertheless be drawn from the same circumstances that gave rise to the 

presumption in the first place‖ (Craig v. Brown & Root, Inc., supra, at p. 421; see 
13

Evid. Code, § 604 [―Nothing in this section shall be construed to prevent the 

drawing of any inference that may be appropriate‖]).

Assuming the results of her breath and blood tests gave rise to a 

presumption she was driving with a BAC of 0.08 percent or more, plaintiff argues 

the testimony of her expert witness, Jay Williams, supplied the necessary contrary 

evidence sufficient to rebut the presumption. By contrast, the DMV argues 

Williams‘s testimony was insufficient, arguing that evidence necessary to rebut 

the presumption must be substantial, i.e., ―  ̳reasonable in nature, credible, and of 

solid value; it must actually be ―substantial‖ proof of the essentials which the law 

requires in a particular case.‘ ‖ Asserting the DMV hearing officer‘s refusal to 

credit Williams‘s views shows his testimony was insubstantial, the DMV argues 

his testimony was accordingly insufficient to rebut the statutory presumption.

The DMV misapprehends Evidence Code section 604. That section 

provides that evidence is sufficient to rebut a presumption if it ―would support a 

finding of [the] nonexistence of‖ the presumed fact. (Italics added.) The most 

reasonable meaning of this phrase is that if the predicate facts are found, Vehicle 

Code section 23152‘s presumption will apply unless the driver presents evidence 

which, if believed, ―would support a finding of [the] nonexistence of‖ the 

presumed fact. This plain meaning of the statutory language is supported by the 

Assembly Committee on Judiciary‘s comment on section 604, which states: 

―Such a presumption is merely a preliminary assumption in the absence of 

contrary evidence, i.e., evidence sufficient to sustain a finding of the nonexistence 

of the presumed fact. If contrary evidence is introduced, the trier of fact must 

weigh the inferences arising from the facts that gave rise to the presumption 

against the contrary evidence and resolve the conflict. For example, if a party 

proves that a letter was mailed, the trier of fact is required to find that the letter 

was received in the absence of any believable contrary evidence. However, if the 
14

adverse party denies receipt, the presumption is gone from the case. The trier of 

fact must then weigh the denial of receipt against the inference of receipt arising 

from proof of mailing and decide whether or not the letter was received.‖ (Assem. 

Com. on Judiciary com., reprinted at 29B pt. 2, West‘s Ann. Evid. Code (1995 ed.) 

foll. § 604, p. 59.)

Viewing the presumption in section 23152, subdivision (b) in this way, and 

assuming without deciding that it applies in administrative per se proceedings,10

we find Williams‘s testimony was sufficient to rebut the presumption that 

plaintiff‘s BAC was at least 0.08 percent at the time she was driving. Williams 

was qualified as an expert in the field and his testimony was clear and direct. If 

believed, his evidence would have justified a conclusion that plaintiff‘s BAC was 

rising at the time of her chemical tests and was thus quite possibly below the 0.08 

percent threshold at the time she had been driving. As a consequence, the DMV 

was required to prove plaintiff‘s BAC at the time she was driving without resort to 

the statutory presumption.

C. The Circumstantial Evidence of Plaintiff’s Intoxication Was 

Relevant and Thus Admissible

Having found the statutory presumption in section 23152, subdivision (b), 

even if applicable, does not control this case, we turn to the main issue presented 

here: Did the DMV hearing officer properly admit and consider non-chemical-test 

 

10 The Legislature might in the future wish to clarify whether it intends that 

the evidentiary presumption in section 23152 applies in administrative per se 

proceedings as well as in ―prosecutions.‖
15

evidence to reach her conclusion that plaintiff was driving with at least a 0.08 

percent BAC?11

The crime of drunk driving is set forth in section 23152 and can be 

established in two ways: Subdivision (a) states that ―[i]t is unlawful for a person 

who is under the influence of any alcoholic beverage to drive a vehicle.‖ To prove 

a violation under subdivision (a), the People must present evidence the driver‘s 

alcohol consumption impaired his or her ability to drive. (People v. McNeal

(2009) 46 Cal.4th 1183, 1197.) Subdivision (b) offers an alternative method of 

proof; it states that ―[i]t is unlawful for a person who has 0.08 percent or more, by 

weight, of alcohol in his or her blood to drive a vehicle.‖ To prove a criminal 

violation under subdivision (b), the People need not prove the accused‘s driving 

ability was impaired or diminished, but only that the driver‘s BAC reached or 

exceeded the prohibited level at the time the accused was driving.

The administrative per se law‘s license suspension provision, although not a 

criminal matter, is linked to the second prong of section 23152.

12 Thus, license 

 

11 Plaintiff notes the DMV hearing officer failed to submit to crossexamination so that it might be determined how she used the circumstantial 

evidence to reach her conclusion to reject the testimony of expert witness Jay 

Williams. This failure, she argues, violated her right to due process of law. 

Although it seems extremely dubious that plaintiff‘s due process rights require the 

hearing officer to testify and submit to plaintiff‘s cross-examination, the record in 

any event reveals no objection on this ground or request that the officer testify. 

Accordingly, plaintiff forfeited this claim.

12 We are not here concerned with the less typical administrative per se 

provisions applicable to underage or commercial drivers, or those on probation for 

drunk driving (see §§ 13353.2, subd. (a)(2) [person under 21 years old with a BAC 

of 0.01 percent or greater], 13353.2, subd. (a)(3) [person driving a vehicle 

requiring a commercial driver‘s license with a BAC of 0.04 percent or greater],

13353.2, subd. (a)(4) [person on probation for drunk driving with a BAC of 0.01 

percent or greater]), or to adults who refuse to submit to, or complete, a chemical 

(footnote continued on next page)
16

suspension under the administrative per se law does not require proof of a person‘s 

impairment to safely operate a motor vehicle due to alcohol consumption, but only 

that the person‘s BAC level was 0.08 percent or more. Section 13382, subdivision 

(a) provides in pertinent part: ―If the chemical test results for a person who has 

been arrested for a violation of Section 23152 or 23153 show that the person has 

0.08 percent or more, by weight, of alcohol in the person‘s blood, . . . the peace 

officer, acting on behalf of the [DMV], shall serve a notice of order of suspension 

or revocation of the person‘s privilege to operate a motor vehicle personally on the 

arrested person.‖ (Italics added.) In this case, the DMV presented the results of 

four chemical tests showing plaintiff‘s BAC was at or above 0.08 percent. Given 

the presentation of these facially qualifying chemical test results, did the hearing 

officer abuse her discretion in concluding that non-chemical-test evidence was 

relevant and thus admissible to bolster or corroborate the chemical test results?

Plaintiff argues reliance on the non-chemical-test circumstantial evidence 

was improper because such evidence cannot by itself establish whether her BAC 

was 0.08 percent, higher than 0.08 percent, or lower than that level. She cites to 

scientific evidence showing that physical manifestations of alcohol intoxication 

can occur at levels much lower than a BAC of 0.08 percent and that observable 

physical symptoms correlate poorly to actual BAC levels. She also argues that 

one study has shown that poor performance on field sobriety tests has a low 

correlation to whether a driver‘s BAC is over 0.08 percent. (Hlastala, Polissar & 

 

(footnote continued from previous page)

test as requested by a law enforcement officer (§ 13353) or to underage drivers 

(§ 13388) or adults on probation for drunk driving (§ 13389) who refuse to submit 

to a preliminary alcohol screening (§ 13353.1, subd. (a)).
17

Oberman, Statistical Evaluation of Standardized Filed Sobriety Tests (May 2005) 

50 J. Forensic Science, No. 3, p. 662.)

Unmentioned is that some studies have reached a contrary conclusion. For 

example, the National Highway Traffic Safety Administration (NHTSA) released 

the results of a study in 1998 that evaluated the accuracy of the standardized field 

sobriety test (SFST) battery at BACs below 0.10 percent. (Stuster and Burns, 

Final Rep. to NHTSA, Validation of the Standardized Field Sobriety Test Battery 

at BACs Below 0.10 Percent (1998).) The NHTSA‘s study found that the battery 

of SFSTs, which includes three of the tests administered to plaintiff (the horizontal 

gaze nystagmus test, the ―walk-and-turn test,‖ and the ―one-leg stand test‖), when 

administered by a trained officer, are ―extremely accurate in discriminating 

between BACs above and below 0.08 percent.‖ (Id., at p. v, italics added.) The 

NHTSA‘s report expressly dispelled a common misapprehension ―that field 

sobriety tests are designed to measure driving impairment.‖ (Id., at p. 28.) 

According to the NHTSA, the SFST battery is instead designed specifically to

―provide statistically valid and reliable indications of a driver‘s BAC, rather than 

indications of driving impairment.‖

We are not here attempting to resolve the scientific debate over the use of 

SFSTs to predict BAC. As plaintiff acknowledges, the test for admissibility of 

evidence is not a strict one: As a general matter, evidence may be admitted if 

relevant (Evid. Code, § 350), and ―  ̳[r]elevant evidence‘ means evidence . . . 

having any tendency in reason to prove or disprove any disputed fact that is of 

consequence to the determination of the action‖ (id., § 210). ―  ̳ ―The test of 

relevance is whether the evidence tends,  ̳logically, naturally, and by reasonable 

inference‘ to establish material facts . . . .‖ ‘ ‖ (People v. Wilson (2006) 38 Cal.4th

1237, 1245.) ―The trial court has broad discretion to determine the relevance of 

evidence [citation], and we will not disturb the court‘s exercise of that discretion 
18

unless it acted in an arbitrary, capricious or patently absurd manner.‖ (People v. 

Jones (2013) 57 Cal.4th 899, 947.)

Past cases applying this standard have found circumstantial evidence of 

intoxication may be admissible when later-administered chemical tests show a 

BAC exceeding the legal limit. In Burg v. Municipal Court, supra, 35 Cal.3d 257

(Burg), decided at a time when the BAC threshold for drunk driving was 0.10 

percent,

13 we explained that the crime of drunk driving set forth in section 23152, 

subdivision (b) ―prohibits driving a vehicle with a blood-alcohol level of 0.10 

percent or higher; it does not prohibit driving a vehicle when a subsequent test 

shows a level of 0.10 percent or more. Circumstantial evidence will generally be 

necessary to establish the requisite blood-alcohol level called for by the statute. A 

test for the proportion of alcohol in the blood will, obviously, be the usual type of 

circumstantial evidence, but of course the test is not conclusive: the defendant 

remains free to challenge the accuracy of the test result, the manner in which it 

was administered, and by whom. (People v. Lewis (1983) 148 Cal.App.3d 614, 

620; accord, Fuenning v. Superior Court (Ariz. 1983) 680 P.2d 121, 127. . . 

[rejecting argument that analogous statute represents  ̳substitution of a machine 

test result for a jury verdict‘ because defendant is given an opportunity to 

challenge accuracy of test result, and state must prove beyond a reasonable doubt 

that defendant‘s blood-alcohol level was 0.10 percent at the time he was driving]; 

Cooley v. Municipality Anchorage (Alaska App. 1982) 649 P.2d 251, 254–255.) 

Of course, both parties may also adduce other circumstantial evidence tending to 

 

13 See former section 23152, subdivision (b), as amended by Statutes 1982, 

chapter 1337, section 1, page 4961. The administrative per se law was enacted 

several years later in 1998. (See Stats. 1998, ch. 118, § 4, pp. 757–758.)
19

establish that the defendant did or did not have a 0.10 percent blood-alcohol level 

while driving. (See, e.g., Fuenning, supra, at p. 130.)‖ (Burg, supra, at p. 266, 

fn. 10, italics added.)

Plaintiff would distinguish Burg, supra, 35 Cal.3d 257, as a case involving 

a criminal drunk driving prosecution, not an administrative per se matter, but if 

non-chemical-test circumstantial evidence of intoxication may be admissible in a 

criminal case where the People‘s burden of proof is beyond a reasonable doubt, we 

see no reason why such evidence would be categorically inadmissible in an 

administrative proceeding where the People‘s burden of proof is only a 

preponderance of the evidence. Decisions in the Courts of Appeal support this 

conclusion. Thus, in McKinney v. Department of Motor Vehicles (1992) 5 

Cal.App.4th 519, the Court of Appeal considered whether sufficient evidence 

supported the suspension of a driver‘s license under the administrative per se law. 

Citing Burg, the McKinney court noted that administration of a chemical test 

(blood, breath or urine) ―is not the only means of establishing that a driver‘s 

[BAC] was .08 or more. [¶] . . . [B]oth parties are free to introduce circumstantial 

evidence bearing on whether the driver‘s [BAC] exceeded the permissible level. 

[Citation.]  ̳Evidence regarding the manner in which a defendant drove, 

performed field sobriety tests, and behaved is admissible and relevant as tending 

to establish that he did or did not have a 0.10 [now 0.08] [BAC] while driving.‘ ‖

(McKinney, at p. 526, fn. 6; see Jackson v. Department of Motor Vehicles, supra, 

22 Cal.App.4th at p. 741 [―circumstantial evidence other than chemical test results 

may properly be admitted to establish a driver had the proscribed level of bloodalcohol at the time of the offense‖]; People v. Randolph (1989) 213 Cal.App.3d 

Supp. 1, 7 [same].) 

Plaintiff argues Burg, supra, 35 Cal.3d 257, is unpersuasive because, apart 

from the single sentence referencing non-chemical-test circumstantial evidence, 
20

the opinion does not elaborate on the use of such evidence to prove a driver‘s 

BAC. But Burg‘s citation to Fuenning v. Superior Court, supra, 139 Ariz. 590

[680 P.2d 121] (Fuenning), following that sentence is significant.

14 In that case, a 

person charged with drunk driving argued that circumstantial evidence ―regarding 

the manner in which he was driving, [and] the manner in which he performed the 

field sobriety tests,‖ while relevant to the issue of whether he drove under the 

influence of alcohol, was ―irrelevant to the question of whether he . . . [was] 

driving with a .10% or greater BAC.‖ (Fuenning, supra, at p. 599.) The Supreme 

Court of Arizona rejected the argument, explaining the evidence was relevant and 

thus admissible: ―We agree with defendant that the only ultimate issue is whether 

defendant had a BAC of .10% or greater. In each case in which a violation of [the 

.10 percent BAC law] is charged, the state will present evidence of the test and the 

issue will be whether the test results were an accurate measurement of the 

defendant‘s BAC at the time of arrest. Typically, defendants will attack the 

margin of error, the conversion rate, the calibration of the test instrument, the 

technique used by the operator, the absorption and detoxification factors, etc. 

Evidence of defendant’s conduct and behavior—good or bad—will be relevant to 

the jury’s determination of whether the test results are an accurate measurement 

of alcohol concentration at the time of the conduct charged. For instance, the test 

in the case at bench was given several hours after the arrest and showed a .11% 

BAC. Defendant attacked the results, presenting evidence regarding margin of 

 

14 Fuenning was later superseded by statute on a different point of law. (See 

State ex rel. McDougall v. Superior Court in and for County of Maricopa (1995) 

181 Ariz. 202, 205–206 [888 P.2d 1389, 1392–1393].) This subsequent history 

does not affect Fuenning‘s discussion of the admissibility of circumstantial 

evidence of intoxication.
21

error, time lapse and other factors. Such evidence might raise considerable doubt 

whether the test result of .11% indicated .10% or greater BAC at the time 

defendant was arrested. Evidence that at that time the person charged smelled 

strongly of alcohol, was unable to stand without help, suffered from nausea, 

dizziness or any of the other ‘symptoms’ of intoxication would justify an inference 

that a test administered some time after arrest probably produced lower readings 

than that which would have been produced had the test been administered at the 

moment of arrest. The converse is also true. Evidence that at the time of arrest 

defendant was in perfect control, displayed none of the symptoms of intoxication 

and had not driven in an erratic manner, is relevant to show that a reading of .11% 

from a test given some time later does not prove beyond a reasonable doubt that 

the defendant was driving with a .10% or greater BAC at the time of his arrest.

Such evidence has been held admissible. [Citations.] Again, evidence is 

admissible when it is relevant.‖ (Fuenning, supra, at p. 599, italics added.) 

Plaintiff argues Fuenning is neither controlling nor even on point because it 

did not address the issue before us in the instant case. Although Fuenning is an 

Arizona case and thus admittedly not controlling here (see Farmers Ins. Group v. 

County of Santa Clara (1995) 11 Cal.4th 992, 1018), it persuasively explains why 

circumstantial evidence of intoxication, while not dispositive, may be relevant and 

thus admissible15 to help interpret the results of a chemical test for a driver‘s 

BAC. Moreover, because the Legislature has prohibited driving with a BAC of 

0.08 percent or higher, that being the threshold at which a person cannot safely 

operate a motor vehicle due to alcohol consumption, circumstantial evidence that 

plaintiff was weaving erratically all over the roadway, smelled strongly of alcohol, 

 

15 To the extent plaintiff argues Fuenning, supra, 139 Ariz. 590, did not 

address the admissibility issue, she is simply incorrect.
22

and failed a battery of field sobriety tests may bolster chemical test results 

showing that she had attained or exceeded that BAC level.

The administrative per se scheme in section 13382 is triggered by a 

chemical test result showing a BAC of 0.08 percent or more, and we do not here 

confront a case in which the DMV failed to present such test results; indeed, the 

DMV produced the results of four such tests. In other words, neither the DMV 

hearing officer nor the trial court considered circumstantial evidence of 

intoxication in the absence of any chemical test results. Although we find nonchemical-test evidence of plaintiff‘s intoxication may be relevant and thus 

admissible in the typical administrative per se proceeding triggered by a BAC of 

0.08 percent or more to help connect those test results to a driver‘s BAC at the 

time she was driving (subject, of course, to the hearing officer‘s routine exercise 

of discretion), we would in any event affirm the hearing officer‘s decision in this 

case because the non-chemical-test evidence was admissible to rebut plaintiff‘s 

proffered defense that her BAC was low at the time she was driving and only later 

rose to exceed the legal limit. Her expert, Jay Williams, testified that, in his 

opinion, the four chemical test results indicated plaintiff‘s BAC was rising at the 

time of the tests; from that supposition, he further deduced that plaintiff‘s BAC 

was below the 0.08 percent threshold at the time she was driving. Even assuming

that non-chemical-test evidence cannot by itself prove a driver‘s exact BAC at the 

moment the driver is stopped by a police officer, in this case plaintiff‘s erratic 

driving, outward appearance of substantial intoxication, implausible story of 

having just turned 21 years old, and was coming from a bar without having 

imbibed alcohol at all, and her failure on multiple field sobriety tests, together tend 

to rebut Williams‘s theory of a rising BAC and corroborate the BAC test results. 

For example, plaintiff‘s extremely erratic driving, observed by Sergeant Martin 

from before the moment he first made contact with her, suggests she was quite 
23

intoxicated from that early point in the timeline and tends to refute the expert‘s 

speculation that her BAC was low at the time she was driving, but rose to 0.08 

percent and above only after she was stopped. Whether the circumstantial 

evidence of plaintiff‘s intoxication was admitted to bolster the results of the 

chemical tests or merely to rebut plaintiff‘s defense of a rising BAC, the hearing 

officer did not act in ―an arbitrary, capricious or patently absurd manner‖ and thus 

did not abuse her broad discretion. (People v. Jones, supra, 57 Cal.4th at p. 947.)

Brenner v. Department of Motor Vehicles (2010) 189 Cal.App.4th 365, 

cited by plaintiff, does not warrant a contrary result. In that case, an expert 

examined the maintenance records for the device used to measure the driver‘s 

breath and opined that it produced slightly elevated results. As the driver‘s test 

results showed a BAC of 0.08 percent exactly, the expert opined the driver‘s 

actual BAC was slightly below the legal limit. Because the trial court in Brenner

had granted the driver‘s petition for a writ, the Court of Appeal was required to 

uphold that decision if supported by substantial evidence. By contrast, the instant 

case comes to us in the opposite procedural posture: the trial court here denied

relief to plaintiff and we are bound to uphold that decision if supported by 

substantial evidence. To the extent the appellate court in Brenner asserted that 

―the impressions of the officer may have a bearing on plaintiff‘s level of 

impairment, [but] they have no bearing on the precise level of his BAC‖ (id. at 

p. 373), the statement must be read in the context of the case: Because the 

chemical tests in Brenner were done on a miscalibrated device used to measure the 

BAC in a breath sample, no accurate chemical test results were presented. No 

such problem exists in the instant case; the DMV presented the results of four 

chemical tests and, although plaintiff‘s expert would have interpreted those results 

to conclude her BAC was rising, he did not testify they inaccurately measured her 

BAC at the time the tests were run. To the extent the court‘s statement in Brenner 
24

v. Department of Motor Vehicles, supra, 189 Cal.App.4th 365, may be taken to 

preclude consideration of non-chemical-test evidence to bolster or corroborate 

chemical test results, we disapprove it.

Having concluded the DMV hearing officer properly admitted the 

circumstantial, nontest evidence of plaintiff‘s intoxication, we also conclude 

substantial evidence supported the trial court‘s decision to deny writ relief, thereby 

sustaining the DMV hearing officer‘s decision to suspend plaintiff‘s license to 

drive. A driver whose license has been suspended under the administrative per se 

law can seek review of the DMV‘s decision by seeking a writ of mandate in the 

trial court. ―In ruling on an application for a writ of mandate following an order of 

suspension or revocation, a trial court is required to determine, based on its

independent judgment,  ̳ ―whether the weight of the evidence supported the 

administrative decision.‖ ‘ ‖ (Lake, supra, 16 Cal.4th at p. 456.) Following the 

trial court‘s denial of the writ, the scope of our review on appeal is limited: ―[W]e 

 ̳need only review the record to determine whether the trial court‘s findings are 

supported by substantial evidence.‘ [Citation.]  ̳ ―We must resolve all evidentiary 

conflicts and draw all legitimate and reasonable inferences in favor of the trial 

court‘s decision. [Citations.] Where the evidence supports more than one 

inference, we may not substitute our deductions for the trial court‘s. [Citation.] 

We may overturn the trial court‘s factual findings only if the evidence before the 

trial court is insufficient as a matter of law to sustain those findings.‖ ‘ ‖ (Lake, 

supra, at p. 457.) 

Applying this standard, we have no trouble concluding substantial evidence 

supported the trial court‘s ruling, for it acted well within its discretion in rejecting

the expert‘s testimony and placing primary emphasis on the four chemical tests 

that showed plaintiff‘s BAC met or exceeded the statutory threshold at the time 

plaintiff was driving. Neither the DMV hearing officer nor the trial court was 
25

required to accept Williams‘s testimony at face value. (People v. Prince (1988) 

203 Cal.App.3d 848, 858 [trier of fact ―is permitted to consider the credibility of 

the expert witnesses, the reasons given for their opinions, and the facts and other 

matters upon which their opinions are based‖]; cf. CALCRIM No. 332 [instructing 

the jury it is not required to accept a proffered expert opinion as ―true or 

correct‖].) Both reasonably relied on circumstantial evidence of plaintiff‘s 

intoxication—her general appearance, the odor of alcohol about her person, her 

erratic driving, and her failed field sobriety tests—to support the accuracy of the 

chemical test results and to reject Williams‘s view of the evidence, including his 

opinion of a rising BAC, as unduly speculative. 
26

CONCLUSION

The judgment of the Court of Appeal is affirmed.

WERDEGAR, J.

WE CONCUR:

CANTIL-SAKAUYE, C. J.

CHIN, J.

CORRIGAN, J.

CUÉLLAR, J.

KRUGER, J.
1

CONCURRING OPINION BY LIU, J.

I write separately to clarify the limited way in which evidence of behavioral 

impairment was relevant in this case to determining whether the driver‘s bloodalcohol concentration (BAC) was 0.08 percent or higher at the time of arrest.

―  ̳Relevant evidence‘ means evidence . . . having any tendency in reason to 

prove or disprove any disputed fact that is of consequence to the determination of 

the action.‖ (Evid. Code, § 210.) Evidence that a driver‘s behavior is not 

impaired tends to prove that her BAC was below 0.08 percent because we can 

rationally surmise, given the Legislature‘s choice of the 0.08 percent BAC 

threshold, that a BAC of 0.08 percent is associated with an unsafe degree of 

impairment. But the converse is not true. Absent foundational evidence, a 

driver‘s impairment does not generally tend to show that her BAC was 0.08 

percent or higher because we have no way of correlating a specific type or degree 

of impairment with a particular BAC in a close case. The fact that 0.08 percent 

BAC is a threshold associated with an unsafe degree of impairment does not imply 

that no impairment occurs below that threshold. Without evidence that correlates 

particular behavioral impairments with particular BAC levels, signs of impairment 

do not generally establish that it is more likely a driver‘s BAC is 0.08 percent as 

opposed to 0.06 or 0.07 percent. In other words, signs of impairment do not 

generally have a tendency in reason to prove a BAC of 0.08 percent or greater.
2

I say ―generally‖ because sometimes evidence of impairment can be so 

extreme — for example, if the driver passed out at the scene of arrest — that the 

trier of fact may infer on the basis of common experience that the driver likely was 

driving with a BAC of 0.08 percent or higher. But there is no evidence of such 

extreme impairment in this case.

Today‘s opinion properly refrains from suggesting that there is a correlation 

between evidence of impairment, including field sobriety test results, and a BAC

of 0.08 percent or greater. The court cites a study commissioned by the National 

Highway Traffic Safety Administration (NHTSA) reporting that at least some field 

sobriety tests, properly administered, may accurately measure a BAC of 0.08 

percent or greater. (Stuster and Burns, Final Rep. to NHTSA, Validation of the 

Standardized Field Sobriety Test Battery at BACs Below 0.10 Percent (1998)

p. v.) But today‘s opinion is careful to express no view about the merits of these 

claims (maj. opn., ante, at p. 17), and other courts have questioned them. In

United States v. Horn (D.Md. 2002) 185 F.Supp.2d 530, for example, the court 

undertook an extensive review of expert testimony and academic literature 

critiquing an earlier NHTSA study and concluded that ―presently there is 

insufficient data to support these claims of accuracy‖ of field sobriety tests in 

predicting BAC. (Id. at p. 556.)

This lack of correlation between evidence of impairment and BAC does not 

mean that such evidence is always irrelevant. As the New Mexico Supreme Court

has explained, ―behavioral evidence by itself cannot be sufficient to show the 

required nexus between a BAC test and an earlier BAC. It may, however, have 

limited relevance when the factors that underlie the shape of the concentration 

time curve [showing the level of alcohol absorption over time] are subject to 

conflicting testimony.‖ (State v. Day (N.M. 2008) 176 P.3d 1091, 1100.)
3

That is precisely how such evidence is relevant in this case. The results of 

the four tests of Ashley Coffey‘s BAC indicated that it was rising, and the parties 

offer competing explanations. Coffey argues that her BAC was in fact rising and 

that her BAC must have been below 0.08 percent at the time of her arrest. By 

contrast, the Attorney General attributes the rising BAC test results to the test‘s 

margin of error (which would explain the 0.01 percent rise within three minutes 

between the first and second breath tests) and to the fact that the last two tests 

were blood tests rather than breath tests and thus produced slightly different 

results. The Attorney General asserts that the testimony of Coffey‘s expert, Jay 

Williams, lacked key findings to support a rising BAC theory, such as when 

Coffey had her last drink before getting behind the wheel, her food intake, her 

weight, and other factors. As the Department of Motor Vehicles (DMV) hearing 

officer concluded, Williams did not show that other experts in the scientific 

community had reached similar conclusions based on facts similar to those in this 

record.

Evidence of Coffey‘s impairment was relevant to deciding which theory of 

rising BAC was more likely correct. Such evidence was relevant in the following 

limited sense: The fact that Coffey did show signs of impairment made her theory 

of rising BAC weaker than if Coffey had not shown signs of impairment at the 

time of her arrest. (See maj. opn., ante, at p. 22 [―[T]he non-chemical-test 

evidence was admissible to rebut plaintiff‘s proffered defense that her BAC was 

low at the time she was driving and only later rose to exceed the legal limit.‖].) 

This point, on which all members of the court agree, renders unnecessary any 

broader suggestion that in a typical administrative per se proceeding, evidence of a 

driver‘s impairment tends to prove a BAC level of 0.08 percent or higher at the 

time of arrest. Here the evidence of Coffey‘s impairment was, like the other 
4

weaknesses in the expert‘s testimony discussed above, relevant to the DMV 

hearing officer‘s conclusion that the rising BAC theory was ―too speculative.‖

Because the evidence of Coffey‘s impairment was relevant in the limited 

way just described, and because the evidence is sufficient to support the 

determinations of the DMV hearing officer and the trial court that Coffey drove 

with a BAC at or above 0.08 percent, I concur in the judgment.

LIU, J.
1

See next page for addresses and telephone numbers for counsel who argued in Supreme Court.

Name of Opinion Coffey v. Shiomoto

__________________________________________________________________________________

Unpublished Opinion

Original Appeal

Original Proceeding

Review Granted XXX 218 Cal.App.4th 1288

Rehearing Granted

__________________________________________________________________________________

Opinion No. S213545

Date Filed: April 6, 2015

__________________________________________________________________________________

Court: Superior

County: Orange

Judge: Robert J. Moss

__________________________________________________________________________________

Counsel:

Law Offices of Chad R. Maddox and Chad R. Maddox for Plaintiff and appellant.

Kamala D. Harris, Attorney General, Alicia M.B. Fowler, Kenneth C. Jones and Kevin K. Hosn, Deputy 

Attorneys General, for Defendant and Respondent.
2

Counsel who argued in Supreme Court (not intended for publication with opinion):

Chad R. Maddox

Law Offices of Chad R. Maddox

5120 E. La Palma, #207

Anaheim Hills, CA 92807

(714) 695-1500

Kevin K. Hosn

Deputy Attorney General

300 South Spring Street, Suite 1702

Los Angeles, CA 90013

(213) 897-2091