Defendant appeals from his conviction, after a jury trial of driving while under the influence of intoxicants. We affirm.
Defendant makes two assignments of error, both of which relate to the court’s instructions to the jury.
First, defendant complains that the instructions twice mentioned that portion of ORS 487.5401 which forbids driving with a blood alcohol level of .10 percent or more, and thus unduly highlighted that portion of the law.
We find no error. In fact, the court’s instructions referred twice to all the elements of ORS 487.540— once to describe the statute under which the defendant was charged, and the second time to describe the state’s burden of proving each material element of the charge.2 Defendant acknowledges that both instructions correctly stated the law. This was an appropriate *854and balanced approach in defining for the jury the issues and the burden which the law places upon the state.
Defendant claims, however, that "* * * giving both instructions * * * resulted in the impression that the breath test was uncontrovertable [sic] evidence.” We are unable to perceive anything in the instructions as given which justifies defendant’s claim, and so reject it.
Defendant further notes, however, that the entire set of instructions was given again in response to a question received from the jury after deliberations had begun:
"Even though the law states that .10 means a person is 'under the influence,’ does this require a juror to go ahead and pronounce the defendant guilty? Can the breathalyzer say .10 or over and still I could come back with a verdict of not guilty? I just would like to have the law explained to me again so that it is perfectly clear to me.” (Emphasis added.)
The trial court’s response to this request was correct: it replayed the tape recording of its earlier instructions. As the emphasized portion of the jury inquiry shows, this was — at bottom — all the jury was requesting.
Defendant disagrees, claiming that the first two sentences of the jury inquiry required a specific response which the instructions could not provide. This brings us to the general theory involved in defendant’s second assignment of error, viz., that ORS 487.540(l)(a) embodies an impermissible conclusive presumption.
There are really two parts to this second contention of defendant:
(1) ORS 487.540(l)(a) constitutes a conclusive presumption, which is impermissible in the criminal law; and
*855(2) ORS 487.540(l)(a) and ORS 487.5453 must be read to permit consideration by the jury of other evidence which might tend to disprove the breathalyzer result.
Defendant’s first point was decided adversely to him in State v. Torrey, 32 Or App 439, 574 P2d 1138, rev den (1978). Driving with a blood alcohol level of .10 percent or greater is an alternative statutory definition of the offense of driving under the influence of intoxicants, not a conclusive presumption.
Defendant’s second point raises a question about a portion of State v. Torrey which, upon reconsideration, we are now convinced was unduly expansive. In Torrey, we held that, where a defendant is charged with driving under the influence of intoxicants under ORS 487.540(1)(a), (driving with a blood alcohol level of .10 or above) rather than (b) or (c), a trial judge could properly refuse to permit a defendant to offer evidence tending to show that defendant at the time *856exhibited no physical symptoms suggesting he was under the influence. Stated this way, the rule of Torrey is too broad. The correct analysis is as follows:
The gravamen of ORS 487.540(l)(a) is driving with a certain blood alcohol level. The legislature has seen fit to forbid this act, without more. The correctness of the evidence tending to establish the blood alcohol level is thus crucial. Equally crucial is defendant’s right to attack the evidence of blood alcohol level. Defendant can do this in one of two ways. First, he can show, by the testimony of those that performed it, that the chemical analysis used in the case was improperly conducted. Second, he can offer circumstantial evidence from other witnesses (including the defendant) to show that there is such a disparity between what the chemical test shows and other facts that one should infer that the test was in some way defective. See State v. Swarengin, 12 Or App 290, 506 P2d 729 (1973) (decided under analogous prior statute).
However, as with any such testimony, a proper foundation must be laid for it. The question then becomes: What is a proper foundation which will permit a jury to consider circumstantial evidence tending to contradict the state’s evidence of a particular blood alcohol reading? This is a question we did not specifically consider in State v. Swarengin, supra.
We think such testimony, where it is specifically offered for the purpose of challenging, by inference, the accuracy of a test which showed a blood alcohol level of .10 percent or above, is relevant only if proper evidence of the relationship between physical size, blood alcohol content and reasonably expected behavior has been introduced so that the jury has some guidelines to follow in assessing the evidence. Such evidence will usually be in the form of expert testimony. Without such an evidentiary predicate, a jury of laymen would have insufficient data to assign any *857real probative value to observations of the physical behavior of the defendant.4
Applying this rule to the present case, and absent any expert testimony of the kind described, defendant would not have been entitled to have the jury initially instructed that they could consider any physical observations which had been made of defendant in determining whether or not they were persuaded as to the correctness of the blood alcohol test result. It follows that the trial judge correctly declined to answer the two intermediate questions posed to him by the jury, since he would then have been giving an instruction unsupported by evidence. His decision to play back the instruction he had previously given was correct.
Affirmed.
"(1) A person commits the offense of driving while under the influence of intoxicants if he drives a vehicle while:
"(a) He has .10 percent or more by weight of alcohol in his blood as shown by chemical analysis of his breath, blood, urine or saliva made under ORS 487.805 to 487.815 and 487.825 to 487.835 or
"Ob) He is under the influence of intoxicating liquor, a dangerous drug or narcotic drug; or
"(c) He is under the influence of intoxicating liquor and a dangerous drug or narcotic drug.
"(2) Driving while under the influence of intoxicants is a Class A traffic infraction.
The court told the jury:
"Oregon law provides that a person commits the offense of driving while under the influence of intoxicants upon a public highway while he was under the influence of intoxicating liquor or had a .10 percent or more by weight of alcohol in his blood as shown by a chemical analysis of his breath.
"First, that the crime, if any, was committed within Lane County, Oregon. Second, that the crime, if any, was committed on or about January 9, 1977, the date alleged in the complaint. Third, that the Defendant drove a motor vehicle upon a public highway, and fourth, that at the time of driving the motor vehicle, the Defendant was under the influence of intoxicating liquor or had a .10 percent or more by weight of alcohol in his blood as shown by a chemical analysis of his breath.” (Emphasis added.)
ORS 487.545, at the time defendant was tried, provided:
"(1) At the trial of any civil or criminal action, suit or proceeding arising out of the acts committed by a person driving a motor vehicle while under the influence of intoxicants, if the amount of alcohol in the person’s blood at the time alleged is less than .10 percent by weight of alcohol as shown by chemical analysis of the person’s breath, blood, urine or saliva, it is indirect evidence that may be used to determine whether or not he was then under the influence of intoxicants.
"(2) Not less than .10 percent by weight of alcohol in a person’s blood constitutes being under the influence of intoxicating liquor.
"(3) Percent by weight of alcohol in the blood shall be based upon grams of alcohol per one hundred cubic centimeters of blood.
"(4) Nothing in this section is intended to limit the introduction of any competent evidence bearing upon the question of whether or not a person was under the influence of intoxicants.”
The 1977 legislature amended the law by inserting new language in subsection (1) and deleting subsection (4):
"(1) At the trial of any civil or criminal action, suit or proceeding arising out of the acts committed by a person driving a motor vehicle while under the influence of intoxicants, if the amount of alcohol in the person’s blood at the time alleged is less than .10 percent by weight of alcohol as shown by chemical analysis of the person’s breath, blood, urine or saliva, it is indirect evidence that may be used with other evidence, if any, to determine whether or not he was then under the influence of intoxicants.” (Emphasis added.)
To the extent that State v. Torrey, supra, creates an absolute rule of inadmissibility, rather than one based upon a requirement of a proper foundation, it is disapproved.