Challenging DUI Chemical Tests

Once the officer determines there is sufficient probable cause to make the arrest, the officer will transport the arrestee to the police station, where they will be asked to choose one of three chemical tests. Most jurisdictions offer the driver the choice of a blood, breath, or urine test. Other jurisdictions only offer blood and breath tests.

Your DUI attorney will be very familiar with these tests and know how to determine their reliability, specifically whether the state’s mandatory test procedures were followed to ensure an accurate reading of your blood alcohol concentration level (BAC).

This article covers how your DUI attorney can challenge the reliability and accuracy of the test results at the time of trial through your lawyer’s cross-examination of the prosecutor’s toxicologist.

Defense Counsel Must Serve Discovery Requests On The Prosectuion

To effectively challenge the test results, your DUI attorney must serve discovery requests on the prosecution requiring them to produce documents showing the exact methods, practices, and protocols used in obtaining the test results.

Challenging Chemical Test Results at Trial

Prosecutor Carries the Burden of Proof

Should your lawyer successfully challenge the reliability and accuracy of the chemical test at trial, under the laws governing the prosecutor’s burden of proof in criminal matters, the prosecution must prove beyond a reasonable doubt that the chemical test was reliable and that the proper test procedures were followed.

Defense Questions That Need Answers Before Trial

Blood test questions

• Was the blood drawn within the time specified by law?
• Was the blood drawn by a person certified by the state or county?
• Was the proper amount and type of preservative used in the blood vial?
• Was the blood adequately stored before the test?
• Is there a sample available for the defense to test independently?
• Are the officials, procedures, and machinery used in the trial all certified by the state or county?
• Can the prosecution prove their chain of custody of the evidence?

Breath test questions

• When was the breath machine last calibrated?
• Was the machine serviced just before or after the test?
• Had the breath machine been certified by the state?
• Was the operator certified on how to operate the breath machine by the state or county?
• What calculations does the machine use to convert air alcohol to blood alcohol?
• Is the machine subject to outside interference from nearby electronic equipment?
• Did the driver belch or burp before taking the test? A burp/belch can bring up alcohol and is detectable by the breath test.
• Did the driver use mouthwash or breath spray (containing alcohol) before taking the test?

Urine test questions

• Did the driver completely void their bladder before he gave the urine sample?
• Did the driver wait the required time before he gave the sample?
• Was the sample stored adequately before testing?
• Is there a sample available for the defense to test independently?
• Are the officials, procedures, and machinery all certified by the state or county?
• Can the prosecution prove their chain of custody of the evidence?

 DUI Criminal Defense Attorney

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