concurring in part and dissenting in part.

I concur with the majority that the conviction in this case must be reversed, because defendant did not waive her right to a jury trial in writing. I disagree, however, with the conclusion that the result of the test of defendant’s breath is admissible without showing that the provisions of ORS 487.815(3)(c) have been complied with and, therefore, dissent from that part of the majority opinion.

The amount of alcohol, if any, in a person’s blood at a given time is a question of fact. The purpose of the requirements written into ORS 487.815 is to ensure that, when the determination of a person’s blood alcohol level is made by testing his breath, the determination is accurate, that is, it is a fact. Before a fact that is the result of scientific testing is admissible, it must be established that correct testing procedures were followed. This is true for any party in any kind of case; prosecutions for DUII are not an exception. The majority would require the state to meet a stricter standard for admissibility of its scientific evidence than that required of the defendant.

Without citing any authority, the majority asserts that in a DUII trial a defendant may put in evidence the results of an independent chemical or blood test “without certification or approval of the test administrators or their methods and machinery.” That statement is at least misleading and, I submit, is inaccurate. Before such evidence may be admitted, a defendant must establish the time and place at which a sample of his blood or other bodily substance was taken, that the time it was taken was reasonably near the time of arrest, that it was taken by a qualified person, that it was analyzed, that the sample *665analyzed was the sample taken near the time of the arrest, that the person who conducted the analysis was qualified to do so, that the procedures used in the analysis were procedures recognized as scientifically reliable, and that the procedures were correctly followed.1

The majority would treat the evidence of a low level of blood alcohol shown by a breath test as if it were an admission by the state against its interest. It is not.

I would hold that the results of a breath test are available to the defendant, as well as to the state, on the same terms; that is, before they are admitted, a foundation showing compliance with the requirements of ORS 487.815 must be established.

Defendant appeals her conviction after trial to the court for driving under the influence of intoxicants. ORS 487.540. She assigns as errors that the trial court (1) heard the case without a jury when there was no written waiver of a jury trial and (2) refused to admit evidence of a. 01 percent breathalyzer test result.

Article I, section 11, of the Oregon Constitution and ORS 136.001 require a written waiver of a jury trial. The state confesses error, acknowledging that no formal, written waiver executed by defendant appears in the trial court file. The conviction must be reversed and the case remanded for new trial. State v. VanLieu, 48 Or App 671, 617 P2d 914 (1980); State v. Miller, 43 Or App 697, 603 P2d 784 (1979).

Because the question will arise on retrial, we address defendant’s second assignment of error. After she was arrested for DUII, defendant submitted to a breathalyzer test at the state’s request. The result showed her blood alcohol level to be .01 percent. At trial, the arresting officer testified concerning defendant’s condition and conduct at the time of her arrest and her performance in field sobriety tests. On cross-examination, defendant attempted to introduce the breath test result to rebut the state’s case by showing that the officer who had administered the test was qualified to do so, that the appropriate test procedure had been followed and that the machine used was the one ordinarily used by the sheriffs office. The state objected to the introduction of the breathalyzer result on the ground that defendant had failed to show sufficient foundation for admission of the test result under the Implied Consent Law, ORS 487.805 et seq, by showing that the machine used had been tested and certified by a trained technician within the 60 days before her breath test. ORS 487.815 (3) (c). The trial court agreed.

The state argues that under ORS 487.8151 the result of a breathalyzer test is not admissible in DUII cases, *661unless it is shown that the test was performed according to approved methods on a certified machine by an individual who has a valid permit. Defendant contends that the requirements of ORS 487.815 apply only when the state seeks to introduce breathalyzer results as proof of a defendant’s guilt, not when a defendant offers evidence of a low test result to rebut the state’s case.

In deciding whether ORS 487.815 should apply to a favorable breath-test result that defendant seeks to introduce, we must first determine the purpose of the Implied Consent Law. Generally, breathalyzer results are offered *662by the state to prove a violation of ORS 487.540(1),2 and their admissibility is restricted only in DUII prosecutions. ORS 487.815 does not apply in any other criminal or civil actions. ORS 487.815(3) (c) places the burden on the state to test and certify the equipment before its regular use and periodically thereafter. Therefore, the statute will generally act to prevent conviction of persons for DUII as a result of faulty equipment or procedures. This is the principal purpose of the statute. See State v. Fogle, 254 Or 268, 274, 459 P2d 873 (1969). Clearly, the purpose of preventing conviction on unreliable evidence does not justify excluding the results of tests performed by the state sought to be introduced by a defendant when the test result has an exculpatory tendency. If the state, in fact, believes the test was unreliable, it may offer evidence to that effect in rebuttal. The trier of fact may or may not believe that evidence. Moreover, it does not necessarily follow that a test result is not accurate merely because the machine on which the test was made has not been tested for accuracy within the time specified. The certification requirement is a condition to the test’s use by the state to convict, not to its use by defendant to cast doubt upon the state’s other proof of intoxication.

Also, a person arrested for DUII may obtain an independent chemical or blood test by a qualified person under ORS 487.810,3 which is admissible without certification or approval of the test administrators or their methods *663and machinery. Defects in such tests presumably go to the weight accorded the evidence, not to its admissibility. It would appear logical that the same should be true for state-administered test results offered by a defendant. Because defendant could introduce uncertified private test results, we perceive no purpose to be served by refusing to permit her to introduce uncertified state test results.4 Similarly, a defendant who has taken a breath test at the request of an officer and obtained a favorable reading would be unlikely to request another test pursuant to ORS 487.810. ORS 487.815 imposes the duty on the state to conduct state-requested tests in compliance with methods approved, and by persons possessing valid permits issued by, the Health Division or the Department of State Police and with equipment tested in accordance with ORS 487.815(3)(c). However, the Implied Consent Law does not require that a defendant prove that a breathalyzer test was administered in compliance with ORS 487.815 before the result can be admitted.

The state has the burden of proof in a criminal case, and a defendant has the right to make the state’s burden of proof as “heavy as possible by calling to the * * * attention [of the trier of fact] any fact which would raise a not completely unreasonable possibility * * * ” inconsistent with guilt. See Byrd v. Lord Brothers, 256 Or 421, 425, 473 P2d 1018 (1970). Although Byrd was a civil case, we perceive no reason why its holding should not apply with equal force in criminal cases. The “fact” defendant seeks to prove is that, in the course of the state’s investigation of her condition immediately following her arrest, one of several tests made by the state produced a result consistent with her sobriety. The possibility that she was not intoxi*664cated is clearly a subject on which she may produce evidence to rebut the state’s case. Certainly she can testify that, at the officer’s request, she submitted to a breathalyzer test and to her recollection of its result. It follows that the test result itself is admissible when offered to impeach the state’s case.

Reversed and remanded for new trial.