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How Can Blood Test Chain of Custody Issues Affect Your DWI Case? 

 Posted on February 21, 2023 in Criminal Defense

Austin Drunk Driving Lawyer

Blood alcohol concentration (BAC) is the measure of alcohol in a person's bloodstream. The two most common ways of measuring BAC in a Texas drunk driving case are breath tests and blood tests. However, for a chemical BAC test to be reliable, there must be an accurate chain of custody.

Chain of custody is the careful tracking and recording of evidence from its collection to its presentation in court. It must be proven that a blood sample was not contaminated or tampered with in any way between the time it was taken and when it arrived at the laboratory for testing. If there are any gaps in this chain of custody, then the evidence may be considered inadmissible.

If you or someone close to you has been accused of driving while intoxicated (DWI), make sure you understand how chain of custody issues can influence your case. It may be possible to get the charges dropped or secure an acquittal if a blood alcohol test was not handled correctly.

Examples of Problems With a Blood Alcohol Test that May Invalidate Results

To convict someone of drunk driving, the prosecution must prove that the person committed the offense beyond a reasonable doubt. Issues with the blood collection process, blood sample storage, or chain of custody of the sample can cast doubt on the test's accuracy and, therefore, the defendant's guilt.

The prosecution must have documentation of the chain of custody of the blood sample from collection to analysis to trial. Chain of custody problems may involve:

  • Uncertainty about when the sample was collected

  • Missing information about who was in possession of the blood sample and when

  • Inadequate labeling and organization of blood sample(s)

  • The possibility that the blood sample was mixed up with other blood samples

  • Inaccurate identification of the person who took the sample

  • Improper handling or storage of the blood sample

If any of these issues arise, the defense attorney may argue that the BAC test results are not reliable and should be excluded from evidence. A skilled lawyer can review the chain of custody and determine if it was improperly handled. If problems exist, they may be able to get the test results suppressed or even get the charges dropped.

Contact an Austin DWI Defense Lawyer

The consequences of a DWI conviction in Texas are serious. If you or someone close to you is facing DWI charges, contact Morales Law Office, Attorneys at Law, PLLC. for legal help. Call our Austin, Texas drunk driving defense attorneys at 512-474-2222. We offer free initial consultations.


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