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What Is Blood Alcohol Content (BAC)?

April 7, 2017 by Mike Worgul in DUI

You may have heard the term blood alcohol content (BAC) in relation to driving under the influence (DUI) of alcohol. But understanding BAC is more than just knowing a number—it can help you comply with the law and even challenge invalid evidence in a DUI case.

If you’re facing DUI charges in Pennsylvania, it’s important to understand how BAC affects your case. Call Worgul, Sarna & Ness, Criminal Defense Attorneys, LLC today at (412) 281-2146 for a free consultation with an experienced Pittsburgh DUI lawyer.

What Is BAC?

BAC is the amount of alcohol in your bloodstream, measured in grams per 100 milliliters of blood. For example, a BAC of 0.08% means there are 8 grams of alcohol per 100mL of blood.

Pennsylvania’s Legal BAC Limits

Drivers 21 and older: A BAC of 0.08% or higher is illegal.
Underage drivers (under 21): Zero tolerance applies, meaning any detectable alcohol in the system can lead to penalties.
Commercial drivers: The legal limit is 0.04% due to stricter federal regulations.

How Is BAC Measured?

Law enforcement determines BAC through breath, blood, or urine tests. Each method has pros and cons:

1. Blood Tests (Most Accurate)

Provides the most precise BAC measurement.
Conducted by certified labs.
Requires consent, refusing can result in legal penalties.
Errors like mishandling or contamination can lead to inaccurate results.

2. Breath Tests (Common, But Less Reliable)

Measures alcohol in breath and converts it to a BAC estimate.
Quick and easy for law enforcement.
Affected by factors like improper calibration, medical conditions, or recent alcohol-containing products (e.g., mouthwash).
Can be challenged in court due to potential inaccuracies.

3. Urine Tests (Least Reliable, Often Inaccurate)

Sometimes used when breath or blood tests aren’t available.
Measures alcohol in urine, then estimates BAC using an average ratio.
Results vary greatly between individuals and may overestimate BAC.
Not as immediate, since alcohol takes time to be processed into urine.

How Does BAC Affect Your Body & Driving Ability?

Alcohol affects people differently, but higher BAC levels generally lead to increased impairment:

0.02% – 0.05%: Mild relaxation, slightly impaired judgment.
0.06% – 0.10%: Reduced coordination, slower reaction times.
0.11% – 0.20%: Slurred speech, balance issues, mood swings.
0.21% – 0.30%: Blackouts, vomiting, motor control problems.
0.31% – 0.40%+: Loss of consciousness, breathing difficulties, risk of death.

Even if you don’t feel drunk, scientific evidence shows that a BAC of 0.08% impairs driving ability – which is why it’s the legal limit.

How BAC Affects DUI Cases

Your BAC can impact a DUI charge in two major ways:

Determining Charges

If your BAC is 0.08% or higher, you will likely be charged with a DUI.
You can still face DUI charges if your BAC is below 0.08%. If officers observe signs of impairment, such as erratic driving, slurred speech, or failed sobriety tests.

Trial Evidence

Prosecutors use BAC test results as key evidence in DUI cases.
A DUI defense attorney can challenge BAC results by questioning test accuracy, equipment maintenance, and legal procedures.

Can BAC Test Results Be Challenged?

Yes! BAC tests are not foolproof, and a skilled Pittsburgh DUI attorney can challenge them by investigating:

Testing accuracy: Were proper protocols followed?
Machine calibration & maintenance: Was the breathalyzer correctly maintained?
Medical conditions: Could a condition (e.g., diabetes, acid reflux) have falsely elevated BAC?
Illegal traffic stops: Did the officer have probable cause to stop you?

Charged with DUI? Contact a Pittsburgh DUI Attorney Today

If you’ve been charged with a DUI in Pennsylvania, don’t assume a high BAC means an automatic conviction. DUI tests can be flawed, and an experienced attorney can challenge the evidence against you.

Call Worgul, Sarna & Ness, Criminal Defense Attorneys, LLC today at (412) 281-2146 today for a free consultation with a knowledgeable Pittsburgh DUI lawyer.

We’ll fight to protect your rights and build a strong defense.