The Davenport case holds that the arresting officer’s written statement is sufficient to support the DMV’s suspension of the defendant’s driver’s license. The Davenport court held that the officer has a duty to administer chemical tests according to methods that are designed to assure reliability. Similarly, California Evidence Code Section 664 gives the presumption that the officer’s official duty has been “regularly performed," thus giving rise to an inference of the reliability of the test.

The result of the above propositions is that the burden of proof shifts to the defendant to show that the officer did not perform the test in a reliable way. The Davenport court held that due process is not offended by placing the burden of rebutting the reliability of chemical tests on the defendant. Law enforcement agencies have an official duty to perform blood-alcohol analyses by reliable methods complying with statutory and regulatory standards. Where there is compliance with regulations that establish standards for the competency of chemical tests, foundation is laid for the admissibility of the test results into evidence. Thus, the test results themselves are deemed legally sufficient evidence.

The defendant has the burden of proof in establishing, through cross-examination of the officer, or by other means, that the official standards were in any way not observed. If the defendant succeeds at bringing into doubt the trustworthiness of the administration of the chemical tests, then the burden of proof shifts back to the police department to prove that the tests were reliable despite the violation.

In a DUI arrest, the police officer fills out a standard DS 367 form, including a sworn statement as to the probable cause and the facts of the arrest. The sworn statement stating that the defendant’s blood alcohol level was at a particular level is bases on reliable testing. In general, the foundational requirements for establishing the reliability of test results consist of a showing that:

1.The testing equipment was in proper working order
2.The test was properly administered
3.The operator of the testing machine was competent and qualified.

Evidence Code Section 664 supports the presumption that the police officer’s official duty has been “regularly performed," meaning that it was performed in regulatory and statutory guidelines. This supports the proposition that the chemical tests have sufficient indicia of trustworthiness justifying reliance upon such test results to support the defendant’s license suspension.