The Importance of Blood Test Accuracy in DUI Cases

When someone is accused of driving under the influence (DUI), a blood test is often used to determine if they were over the legal limit. These tests play a crucial role in DUI cases, but they’re not always perfect. Let’s explore why the accuracy of blood tests is so important and what can go wrong.

Why Blood Tests Matter

Blood tests are considered one of the most reliable ways to measure how much alcohol or drugs are in a person’s system. Unlike breath tests, which estimate blood alcohol content (BAC) indirectly, blood tests measure it directly. This makes them a powerful tool for both prosecutors and defense attorneys in DUI cases.

In most states, including Arizona, it’s illegal to drive with a BAC of 0.08% or higher. For commercial drivers, the limit is even lower at 0.04%. These precise numbers show why accurate testing is so important – even a small error could mean the difference between a conviction and an acquittal.

How Blood Tests Work

When someone is suspected of DUI, they might be taken to a hospital or clinic for a blood draw. A trained professional, usually a phlebotomist, takes a small sample of blood. This sample is then sent to a lab for analysis.

In the lab, scientists use special machines to measure the amount of alcohol or drugs in the blood. They look at how many grams of alcohol are in 100 milliliters of blood. The result is given as a percentage, like 0.08%.

Potential Problems with Blood Tests

While blood tests are generally reliable, they’re not perfect. Several things can go wrong:

• Contamination: If the equipment used to take the blood sample isn’t clean, it could affect the results.
• Improper Storage: Blood samples need to be stored correctly. If they’re not kept at the right temperature, the results might not be accurate.
• Lab Errors: Sometimes, mistakes happen in the lab. Equipment might not be calibrated correctly, or a technician might make a mistake.
• Timing Issues: Alcohol levels in the blood change over time. If there’s a long delay between when someone is driving and when the blood is taken, the test might not accurately reflect their BAC while driving.
• Chain of Custody Problems: The blood sample needs to be carefully tracked from the moment it’s taken until it’s tested. If there are gaps in this “chain of custody,” it could raise doubts about the reliability of the test.

Real-Life Example: The Colorado Bureau of Investigation Case

In 2021, a concerning situation came to light in Colorado. The Colorado Bureau of Investigation (CBI) admitted that at least 56 of the DUI blood tests they conducted in a six-month period were incorrect.

These weren’t small errors. In each of these 56 cases, the initial results showed lower alcohol levels for the drivers than when additional quality assurance retesting occurred. This means that some drivers might have faced less severe charges than they should have based on their actual BAC.

Let’s break down what happened:

1. The CBI opened new labs in Pueblo and Grand Junction in July 2015.
2. Between July 2015 and early 2021, these labs conducted about 1,500 DUI blood tests.
3. In September 2021, the CBI acknowledged that at least 56 of these tests (about 4% of the total) were incorrect.
4. An independent chemist, Dr. Pat Sulik, checked 16 blood samples from the CBI. Of these 16, seven had significant discrepancies.
5. Dr. Sulik noted that in at least one case, a suspect would have faced more serious charges if the initial CBI test had been correct.

This case shows how even established labs can make mistakes, and why it’s so important to have checks and balances in place.

The Impact of Inaccurate Tests

Inaccurate blood tests can have serious consequences. If a test shows a higher BAC than reality, an innocent person might be convicted of DUI. On the other hand, if a test shows a lower BAC, someone who was driving drunk might get off with a lesser charge or no charge at all.

These errors don’t just affect individual cases. They can undermine public trust in the justice system. If people don’t believe that DUI testing is accurate, it could make it harder to enforce drunk driving laws and keep roads safe.

Protecting Against Errors

Given the importance of accurate blood testing, there are several safeguards in place:

• Quality Control: Labs have strict procedures to ensure accuracy. This includes regularly calibrating equipment and double-checking results.
• Chain of Custody: There are detailed rules about how blood samples should be handled, stored, and tracked.
• Defense Strategies: DUI defense attorneys often scrutinize blood test results. They might challenge how the blood was collected, stored, or analyzed.
• Independent Testing: In some cases, defendants can have their blood sample independently tested to verify the results.

Conclusion

Blood tests play a vital role in DUI cases, but they’re not infallible. Understanding the potential for errors helps ensure that justice is served accurately. Whether you’re a driver, a law enforcement officer, or just a concerned citizen, knowing about these issues can help you make informed decisions and advocate for fair treatment under the law.

Frequently Asked Questions

1. How long after drinking can a blood test detect alcohol?
   Blood tests can detect alcohol for up to 12 hours after drinking, depending on how much was consumed.
2. Can I refuse a blood test if I’m suspected of DUI?
   In most states, you can refuse, but this often leads to automatic license suspension and can be used against you in court.
3. Are blood tests more accurate than breathalyzers?
   Generally, yes. Blood tests provide a direct measurement of BAC, while breathalyzers estimate it indirectly.
4. How long does it take to get blood test results in a DUI case?
   It usually takes a few days to a few weeks, depending on the lab’s workload and procedures.

Can medications affect blood alcohol test results?
Some medications can interfere with blood alcohol testing, potentially leading to false positives or inaccurate readings.