Opinion ID: 2635209
Heading Depth: 2
Heading Rank: 2

Heading: Development of California Law Regarding Partition Ratio Evidence

Text: California's first drunk driving statute, enacted in 1913, prohibited any intoxicated person from driving a motor vehicle on a public highway. (Stats. 1913, ch. 326, § 17, p. 646; see Burg v. Municipal Court (1983) 35 Cal.3d 257, 262 [198 Cal.Rptr. 145, 673 P.2d 732].) The prohibition was later redefined as driving under the influence of alcohol. To be `under the influence' within the meaning of the Vehicle Code, the liquor or liquor and drug(s) must have so far affected the nervous system, the brain, or muscles as to impair to an appreciable degree the ability to operate a vehicle in a manner like that of an ordinarily prudent and cautious person in full possession of his faculties. [Citations.] ( Byrd v. Municipal Court (1981) 125 Cal.App.3d 1054, 1058 [178 Cal.Rptr. 480], italics omitted.) In 1969 the Legislature enacted a statutory presumption that a driver was under the influence if the driver's blood contained 0.10 percent or more, by weight, of alcohol. (Stats. 1969, ch. 231, § 1, p. 565; Burg v. Municipal Court , at p. 263.) However, [e]ven these laws, which considerably assisted the prosecution of `driving under the influence' cases, proved inadequate in many respects. Under them, the ultimate question was defined in terms of the defendant's subjective behavior and condition: `Was the defendant under the influence at the time he drove?' Celerity and certainty of punishment were frustrated by the ambiguity of the legal criteria; no matter what his bloodalcohol level, a defendant could escape conviction merely by raising a doubt as to his intoxication. [Citations.] ( Burg v. Municipal Court , at p. 263.) These difficulties led the Legislature to create a new crime. Section 23152(b), added in 1981, made it unlawful for a person to drive with a blood-alcohol level of 0.10 percent or more, by weight, and specified that, percent, by weight, of alcohol shall be based upon grams of alcohol per 100 milliliters of blood. (Stats. 1981, ch. 940, § 33, p. 3578.) To secure a conviction for this new per se DUI offense, the prosecution no longer had to prove the accused driver was actually impaired at the time of the offense, but only that he drove with a blood-alcohol level at or exceeding 0.10 percent. ( Burg v. Municipal Court , at p. 265.) In 1989, the Legislature further strengthened our state's DUI laws by lowering the punishable blood-alcohol threshold from 0.10 percent to 0.08 percent. (Stats. 1989, ch. 1114, § 27, p. 4080; see People v. Ireland (1995) 33 Cal.App.4th 680, 689 [39 Cal.Rptr.2d 870].) Thus, after 1981 there were two parallel statutes making it a crime to drive while intoxicated. The generic DUI provision (§ 23152(a)) retained the historical approach, requiring proof that the defendant was actually impaired by his drinking. The per se DUI statute (§ 23152(b)) simply required proof that the defendant had been driving with a blood-alcohol level over the legal limit. If the limit was exceeded, the statute was violated, and no additional proof of the defendant's impairment was required. Throughout this time, both the per se DUI offense and the presumption of intoxication applicable to the generic DUI offense were defined based on measurements of blood alcohol. As a result, whenever a defendant elected to have a breath test instead of a blood draw, it was necessary to convert the breath results into an equivalent blood-alcohol percentage. ( Bransford, supra, 8 Cal.4th at pp. 888-889; People v. Ireland, supra, 33 Cal.App.4th at p. 689.) A Department of Health Services regulation required that this conversion be made using a partition ratio of 2,100 to 1. (Cal. Code Regs., tit. 17, § 1220.4, subd. (f).) [7] The mandated use of a standard partition ratio, in the face of scientific knowledge that such ratios vary greatly, provided fertile ground for defense arguments challenging the reliability of breath test results. Initially, courts permitted defendants to show only that their personal partition ratio differed from the norm. ( Bransford, supra, 8 Cal.4th at p. 889.) Applying the judicially created rule of convenience, these courts placed the burden on the defendant to produce evidence of a nonstandard personal ratio because this fact was considered to be peculiarly within the defendant's knowledge. ( People v. Pritchard, supra, 162 Cal.App.3d at p. Supp. 16; see People v. Gineris (1984) 162 Cal.App.3d Supp. 18, 23 [209 Cal.Rptr. 317]; People v. Herst (1987) 197 Cal.App.3d Supp. 1, 3-4 [243 Cal.Rptr. 83].) Later courts questioned this application of the rule of convenience when confronted with evidence showing that an individual's partition ratio can vary from time to time due to the influence of numerous external factors. (See, e.g., People v. McDonald, supra, 206 Cal.App.3d at p. 883.) This evidence directly contradicted something the Pritchard line of cases had apparently assumed: that one's partition ratio is constant and can be measured by the defendant. ( Ibid. ; see also People v. Lepine, supra, 215 Cal.App.3d at pp. 97-99.) Because partition ratios may vary depending on many factors, reliable measurements may be difficult and costly to acquire. Thus, some courts reasoned that defendants did not have substantially better access to evidence of their personal partition ratios and could not be expected to carry the burden of production on the issue. ( People v. McDonald , at p. 883; People v. Lepine , at pp. 99-101; People v. Thompson (1989) 215 Cal.App.3d Supp. 7, 13 [265 Cal.Rptr. 105].) Further, having freed defendants from the rule of convenience, these courts saw no reason to exclude general partition ratio evidence describing the variability of partition ratios among the general population. ( People v. Lepine , at p. 100; People v. Thompson , at pp. Supp. 13-14; People v. Cortes (1989) 214 Cal.App.3d Supp. 12, 18 [263 Cal.Rptr. 113].) After citing a string of out-of-state decisions permitting such evidence, one court reasoned: [I]t seems clear from the evidence submitted in this case and from a host of opinions in this and other states, that the partition ratio may vary from time to time and from individual to individual. This being the case it is appropriate a jury be allowed to consider that fact. We trust in the general rules of evidence, the preparation of counsel and the good judgment of trial judges to insure that this question of partition ratio variability is presented to jurors in a proper, complete and understandable form. ( People v. Lepine , at p. 100, fn. omitted.) (1) The Legislature responded swiftly to these developments. In April 1989, legislators amended a pending Senate Bill on a related topic to specify for purposes of the per se DUI offense and the presumption of intoxication that the percentage of alcohol in a person's blood is to be based upon grams of alcohol per 100 milliliters of blood or grams of alcohol per 210 liters of breath. (Sen. Amend. to Sen. Bill No. 1119 (1989-1990 Reg. Sess.) Apr. 27, 1989, p. 23; Stats. 1989, ch. 1114, §§ 24-25, pp. 4078-4079 [amending § 23152(b)]; Sen. Amend. to Sen. Bill No. 1119 (1989-1990 Reg. Sess.) Apr. 27, 1989, p. 26; Stats. 1989, ch. 1114, §§ 34-35, pp. 4085-4086 [amending former § 23155, subd. (b)].) In so doing, the Legislature codified 2,100 to 1 as the partition ratio to be used in converting breath test results into blood-alcohol levels. As we observed in Bransford, supra, 8 Cal.4th at page 890, scant explanation for these amendments appears in the legislative history of Senate Bill No. 1119 (1989-1990 Reg. Sess.), but more illumination can be found in the history of Assembly Bill No. 4318 (1989-1990 Reg. Sess.), enacted as Statutes 1990, chapter 708, section 1, page 3289. The purpose of Assembly Bill No. 4318 was to accelerate the effective date of the partition ratio amendments to section 23152(b) that had been enacted by passage of Senate Bill No. 1119. (Assem. Com. on Public Safety, com. on Assem. Bill No. 4318 (1989-1990 Reg. Sess.) as introduced May 15, 1990; see People v. Ireland, supra, 33 Cal.App.4th at p. 691.) Committee reports concerning this bill evince the Legislature's desire to prohibit challenges to breathtest results based on the partition ratio. For example, the Assembly Committee on Public Safety observed that [a]ttacks on the partition ratio may result in expensive and time consuming evidentiary hearings and undermine successful enforcement of driving under the influence laws. (Assem. Com. on Public Safety, com. on Assem. Bill No. 4318 (1989-1990 Reg. Sess.) as introduced May 15, 1990, p. 2.) The express purpose of Assembly Bill No. 4318 was to [e]liminate the need for conversion of a breath quantity to a blood concentration of alcohol by statutorily defining driving under the influence in terms of the concentration of alcohol found in the breath when breath analysis is used. ( Ibid. ; see also Sen. Rules Com., Off. of Sen. Floor Analyses, Rep. on Assem. Bill No. 4318 (1989-1990 Reg. Sess.) Aug. 9, 1990, p. 1.) The Legislature accomplished this purpose by defining the offense of per se DUI in terms of a prohibited level of blood alcohol or breath alcohol. As we explained in Bransford, supra, 8 Cal.4th at page 890, the amendment of section 23152(b) providing for an alternative measurement based upon breath changed the definition of the offense. In the per se DUI statute, the Legislature has set a legal limit on permissible blood alcohol and has defined how that limit is to be measured in a breath sample. If the limit, measured as the statute sets out, is exceeded, the statute has been violated. Because section 23152(b) now defines the offense of per se DUI as the presence of a prohibited level of alcohol in either 100 milliliters of blood or 210 liters of breath, a conversion from breath to blood-alcohol concentration is no longer required to establish guilt. Accordingly, evidence attacking the standard partition ratio is no longer relevant in a per se DUI prosecution because the Legislature has codified the 2,100-to-1 ratio as part of the offense. ( Bransford, at pp. 890-892.) Assembly Bill No. 4318 (1989-1990 Reg. Sess.) did not amend former section 23155, however. [8] The bill amended only the per se DUI offense (§ 23152(b)) and a similar offense of per se DUI causing bodily injury (§ 23153, subd. (b)). (Stats. 1990, ch. 708, §§ 1-4, pp. 2870-2872.) Thus, committee statements reflecting the Legislature's desire to end the conversion of breath results to blood alcohol were all made in regard to changing the definition of the per se DUI offense. No legislative history clarifies exactly what the Legislature intended when it amended the presumption of intoxication applicable to generic DUI cases