Admissibility of Blood Alcohol Tests in Drunk Driving Cases

All 50 states and the District of Columbia have enacted statutes requiring a motorist arrested for drunk driving to submit to a chemical blood test. These statutes are known as "implied consent" laws. Under these laws, a motorist suspected of driving under the influence of alcohol is deemed to have consented to a chemical analysis test designed to measure blood alcohol content level.

Courts have generally held that in a prosecution for driving while intoxicated or under the influence of intoxicating liquor, evidence as to the alcoholic content of a specimen of the motorist's blood, as determined by scientific analysis, and expert opinion testimony as to what the presence of the alcohol in the blood indicates, are admissible as evidence of intoxication. Nevertheless, courts will hold that the evidence derived from the test is admissible only if certain statutory prerequisites are met. What are these prerequisites? First, the state must establish that the sample tested is the same sample withdrawn from the motorist. This is proven by establishing the chain of custody of the sample. Next, the state must prove compliance with all of the administrative procedures specified under the implied consent statutes. Generally, the state must prove that the proper person withdrew the sample for chemical testing (e.g., physician, nurse, laboratory technician, etc.) and the test was performed in accordance with the approved quality assurance and quality control guidelines.

In defending a drunk driving case, the defense can raise the question of compliance with the procedures before any evidence relating to the blood alcohol is admitted. After the defense has raised the compliance issue and objected to the admissibility of the blood alcohol content evidence, the burden of proof will shift to the state to prove beyond a reasonable doubt that the state has complied with all the relevant procedures. If the defense is able to establish noncompliance with some of the requirements for the collection and processing of the sample, the court may schedule a hearing to determine if the foundational facts for admissibility have been proven.

Lastly, if the state presents expert testimony regarding the blood test results at trial, cross-examination or voir may be used by the defense to challenge the expert's qualifications to testify to the test results. If the expert lacks the requisite qualifications, another key component of the state's foundation for admissibility of the test is missing.