People v. Lepine

Citations: 215 Cal. App. 3d 91; 263 Cal. Rptr. 543; 1989 Cal. App. LEXIS 1082Docket: D008908

Court: California Court of Appeal; October 31, 1989; California; State Appellate Court

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In the case of The People v. Amy Jo Lepine, the California Court of Appeals addressed the admissibility of evidence relating to the partition ratio used for converting breath alcohol concentration to blood alcohol concentration in DUI prosecutions under Vehicle Code section 23152, subdivision (b). The court clarified that the defense is not limited to proving that the defendant's specific partition ratio differed from the standard ratio of 2,100 to 1, as defined by California Code of Regulations section 1220.4. Instead, the defense may present general evidence regarding the variability of partition ratios without needing to directly link it to the defendant's individual circumstances. Lepine was charged with driving under the influence, with her breath test indicating a blood alcohol content of 0.13, based on the aforementioned conversion ratio. The defense intended to challenge this ratio through cross-examination of prosecution experts and by presenting testimony from a forensic scientist. The prosecution objected to these challenges, claiming they were irrelevant unless connected to Lepine's actual partition ratio at the time of the test. The court ultimately allowed the defense to pursue broader evidence on the topic.

The expert testified that the 2,100 to 1 partition ratio for blood alcohol content is not fixed, varying among individuals and over time. If an individual's true ratio is less than 2,100 to 1, a machine calibrated at this ratio would yield an inaccurately high blood alcohol reading. Accurate determination of an individual's partition ratio requires both blood and breath samples, as this ratio is influenced by several factors, including alcohol absorption, lung temperature, exhalation dynamics, humidity, mucus presence, and hematocrit levels. After-the-fact determination of an individual's partition ratio is not feasible, although general range testing can be conducted later, costing around $600 for a single test and approximately $6,000 for a series. The expert indicated that the average partition ratio is 2,286 to 1, with 68% of the population falling between 2,040 to 1 and 2,420 to 1, and 95% within 1,800 to 1 and 2,660 to 1.

The trial court denied defense evidence regarding partition ratio variability, relying on precedents from People v. Pritchard and People v. Gineris, which deemed such evidence irrelevant. These cases highlighted issues with the reliability of breath test results converted to blood alcohol percentages based on a variable partition ratio. In Pritchard, it was noted that the testing machine had an error margin, and the conversion ratio's variability could cast doubt on the accuracy of blood alcohol level determinations. The defendant argued that the breath test results did not sufficiently prove his blood alcohol level exceeded 0.10 percent, given the potential for error in the conversion ratio. The appellate court later reversed the trial court's decision and transferred the case for further consideration.

In Gineris, evidence indicated that the partition ratio used to convert breath alcohol findings to blood alcohol content (BAC) was an average, with an individual margin of error of up to 50%. The defendant's BAC was calculated at 0.11, but the expert testified that due to the testing machine's error margin, variability in individual partition ratios, and the time elapsed between driving and testing, it could not be confirmed beyond a reasonable doubt that the defendant had a BAC of 0.10 or higher while driving. In Pritchard, the defendant referenced People v. Campos, which identified an inherent inaccuracy of plus or minus 0.005% in blood tests for intoxication under former Vehicle Code section 23126. The Campos court concluded that because of this inaccuracy, it was improper to instruct the jury that a BAC of 0.10% or more created a presumption of being under the influence, as the true BAC could be lower. The court emphasized that the prosecution must prove the underlying fact of intoxication beyond a reasonable doubt before applying such presumptions. Pritchard's defendant argued that the same rationale should apply to the error rate in the partition ratio for breath-to-blood conversion, asserting insufficient evidence for a BAC of 0.10% or greater. The Pritchard court framed the issue as whether the 10% error margin in the partition ratio should be considered in determining the defendant's BAC. The court noted that while the prosecution could assess the testing machine's error, only the defendant could provide evidence of his actual partition ratio. Invoking the "rule of convenience," the court suggested that the defendant bore the burden of producing evidence regarding his specific partition ratio, as such information was uniquely within his knowledge, while it would be challenging for the prosecution to disprove its existence.

The court in Pritchard established the rule of convenience, presuming a defendant to have a 2,100 to 1 partition ratio unless he presents specific evidence of his own ratio. General evidence of possible error was deemed insufficient to rebut this presumption. The court concluded that adequate evidence supported the conviction, despite expressing concerns about Pritchard's reasoning, particularly the lack of support for the premise that only specific evidence can challenge the presumption. The issue at hand was whether substantial evidence existed to uphold the conviction given the defendant's argument regarding blood alcohol calculation errors. The court found no substantial evidence question arose since the relevant evidence (the defendant's specific partition ratio) had not been provided. The Pritchard opinion did not justify the requirement for specific evidence over general evidence. The Attorney General argued that regulations defining the partition ratio created a presumed fact that defendants must specifically challenge, but the court disagreed, finding no legislative intent for such a presumption in the Health and Safety Code. The court noted that the Legislature has clearly established presumptions in alcohol-related crimes, which was not the case here. Concerns regarding the Pritchard ruling were echoed in People v. McDonald, where expert testimony indicated that while individual partition ratios could vary, asserting the same ratio at the time of arrest was speculative and costly to test.

The jury in the McDonald case received an instruction that presumed a defendant's breath to blood partition ratio to be 2,100 to 1 unless evidence to the contrary was presented. The court found this instruction erroneous, referencing prior cases including Pritchard, Gineris, and Herst, noting that only Herst addressed the appropriateness of such instructions. None of these cases provided admissible evidence that an individual's partition ratio is variable over time, and while evidence was disallowed in Herst, no objection was raised against the defense expert's testimony in McDonald. The defense expert argued that measuring an individual's partition ratio was speculative, contradicting the prosecution's claim of a constant ratio, which the prosecution's expert admitted could fluctuate due to external factors. The court highlighted the importance of the defense expert's testimony against the assumptions of the prior cases regarding partition ratio constancy. It emphasized that the rule of convenience should not apply unless the exonerating fact is uniquely within the defendant's knowledge, which was not the case here. The court indicated that while McDonald does not settle the admissibility of general evidence on partition ratio variability, it hints that such evidence should be admissible. Furthermore, this issue is not limited to California, as other states have acknowledged partition ratio variability, generally deeming it relevant to the weight of breath test evidence rather than its admissibility. The prosecution's argument against allowing evidence of variability was viewed as an attempt to maintain an unfair advantage rather than rectify an imbalance. The court asserted that juries should be allowed to consider partition ratio variability, trusting in the legal process to present this evidence appropriately. Ultimately, the case raises the issue of whether the rule of convenience is valid if general evidence of partition ratio variability is deemed inadmissible.

The rule of convenience is evaluated in relation to presenting individual partition ratio evidence in this case. It is determined that the rule is misapplied here, as the initial burden of producing evidence can be placed on the accused if they have easy access to it and if doing so is not overly burdensome. This rule typically applies when the existence of a license or permit is difficult for the prosecution to prove. However, in this case, the evidence regarding partition ratios is expensive to obtain and subject to variability. Consequently, the trial court's exclusion of the defense from cross-examining the prosecution's expert on this variability and from presenting related evidence was erroneous. The appellate court finds no need to address the appellant's additional constitutional arguments, leading to a reversal of the judgment. The denial of the respondent's petition for review by the Supreme Court occurred on February 21, 1990. Various cases from other jurisdictions are referenced to illustrate differing approaches to partition ratio variability. Additionally, the Attorney General indicated that the Appellate Department of the Los Angeles County Superior Court has abandoned the previously adopted rule of convenience, but the court declines to reject the reasoning of the case cited by the Attorney General.