In a prosecution for Vehicle Code section 23152 subdivision (a) (“generic DUI”), evidence of a defendant’s personal partition ration, but not evidence of the general variability in partition ratios, is relevant and admissable in a prosecution for violation of section 23152(a). Under subdivision (a) of section 23152, it is unlawful to drive under the influence of alcohol. The amount of alcohol in a person’s blood, as shown by blood, breath, or urine tests, gives rise to various permissive presumptions as to whether the person was under the influence which can be rebutted. (Veh. Code, sec. 23160.) Breath testing devices use a mathematical constant to approximate the percentage of alcohol in the blood, based on the amount measured in the breath, with a presumptive blood-breath partition ratio of 1:2,100 (i.e., the same amount of alcohol found in 2,100 milliliters of a person’s breath would be found in a milliliter of the person’s blood). Partition ratios vary in the same individual on the basis of such factors as body temperature, time the alcohol is consumed in relation to when it’s measured, etc. Because generic DUI is concerned with the ultimate fact of intoxication, a defendant’s personal partition ratio is relevant. People v. Bransford (1994) 8 Cal.4th 885 is inapplicable as it deals with subdivision (b), or per se DUI (driving with .08% or greater alcohol). In this case, although it was error to exclude partition ratio evidence, the error was harmless because there was other strong evidence that appellant was driving under the influence meeting the Watson standard. (People v. Watson (1956) 46 Cal.2d 818.)