Free Consultation:
610-436-1410
Free Consultation:
610-436-1410Many people believe that BAC tests are indisputable and guarantee a conviction in Pennsylvania DUI cases. While they’ve certainly been painted that way, and both the police and prosecutors often view BAC as conclusive proof of impairment, BAC tests are not beyond dispute. They, just like almost any other medical test, do have a margin of error. Before you give up on your DUI case because of a supposedly high BAC result, learn more about these tests and your legal options.
As a member of the National College for DUI Defense and previously ranked among the 10 best by the American Institute of DUI/DWI Attorneys, Chester County attorney Michael Skinner has extensive experience in this area of law and can pinpoint the inaccuracies in both breath and blood chemical test devices.
To discuss how you can overcome a potentially faulty BAC result and avoid the consequences of DUI, call (610) 436-1410 to schedule a free consultation.
Perhaps the most reliable Blood Alcohol Concentration (BAC) test is a blood test. This means that it is often the most difficult to challenge in court. However, there are still factors that can impact the validity of a blood BAC screening, like the validity of the warrant, the chain of evidence with the lab, and possible contamination.
Breathalyzer tests conducted at a medical facility or police station also tend to be highly accurate. Don’t confuse these with roadside breath tests, which are optional and much more flawed. Although the mandatory breathalyzer tests are likely to be accurate, they still need to be maintained and are prone to inaccuracies.
Some breath screening devices are much more likely to have serious errors that could lead to an unfair conviction.
Roadside breathalyzer tests are known for being unreliable. Portable Breath Test devices are not always properly calibrated and maintained to produce accurate results. These tests are designed to gather enough evidence to arrest you. They are often used with Field Sobriety Tests (FSTs) to give officers probable cause to place you under arrest. Once you have been booked at the station, officers may use breathalyzers, whose results can be submitted in court as evidence you were driving under the influence. These machines need to be calibrated often, so the courts favor them over the roadside tests. If you are subjected to a breathalyzer in the police station, the officers must read you your rights and the civil penalties for refusing the test.
While blood tests are generally more reliable than breath tests, they are also more invasive. These tests can check your BAC and also identify drugs and the amount of drugs in your system. Because these tests are more stringent, they can only be used if officers have reason to believe you were under the influence while driving and if you give consent for the test; the officer gets a search warrant authorizing a blood draw; or circumstances demand immediate action to take blood for an accurate test before a warrant is secured.
Urine screenings are notoriously unreliable. Pennsylvania no longer allows their results to be used as evidence in DUI cases. These screenings do not reveal the true level of inebriation. The amount of alcohol in your urine may not match your true BAC.
BAC tests, like blood tests for example, can be compromised by using an expired test kit, a sample drawn incorrectly, or by improperly handling the blood sample. Additionally, consumption of certain substances or medications could change the test results.
Breathalyzer tests rely on machine accuracy. If the machine is not cleaned, maintained, and calibrated on a precise schedule, it can produce inaccurate readings.
Most BAC test errors happen because of:
Many who are accused of driving under the influence do not know that these test results can be challenged and may even be unusable in court. Working with an attorney with extensive knowledge of local DUI laws and procedures is essential.
Even a reading far above Pennsylvania’s legal limit is not the last word on your case. Quick action and the right strategy can cast doubt on flawed results and shift the leverage back in your favor.
Gather every document or recording tied to your arrest—citation, chemical‐test consent form, hospital paperwork, body‑cam footage, and even receipts showing when you last ate or took medication. Pennsylvania’s discovery clock starts running soon after arraignment, so locking down evidence early keeps it from disappearing or being “overlooked.”
You are entitled—through a formal discovery demand or subpoena—to see the breathalyzer’s service history. Missing entries, overdue calibrations, or expired mouthpieces can be enough for a judge to question the machine’s reliability and exclude the test.
If a blood draw was taken, the lab typically seals a second vial. Having an accredited private lab run its own analysis—often for a few hundred dollars—can reveal contamination or show a lower blood‑alcohol concentration that aligns with your recollection of events.
Armed with maintenance gaps, chain‑of‑custody breaks, or conflicting lab findings, your attorney can ask the court to suppress—or at least limit—the prosecution’s use of the BAC number. Without that keystone piece of evidence, the Commonwealth may have little choice but to reduce or dismiss the charge.
Portable breath tests (PBTs) used roadside are generally not admissible as proof of intoxication at trial; they serve only to establish probable cause for an arrest. The prosecution must rely on station breath tests or blood analyses for courtroom evidence.
Infrared and fuel‑cell breathalyzers maintained at police stations are usually reliable, but they still show a wider margin of error than a properly handled blood test. Blood analysis remains the “gold standard,” though it, too, can be challenged for warrant defects, chain‑of‑custody breaks, or contamination.
Under Pennsylvania Rule 573, your attorney can subpoena the device’s calibration logs, service dates, operator certification, and mouthpiece replacement history. Missing or out‑of‑date records often form the basis for a motion to suppress the BAC reading.
Yes. Gastroesophageal reflux disease (GERD), untreated diabetes (acetone buildup), and ketogenic diets can all introduce mouth or breath compounds that some machines misinterpret as ethanol, inflating the reported BAC.
Urine testing was deemed too unreliable because alcohol concentrates in urine later than in blood, creating misleadingly high or low readings. Following cases like Commonwealth v. Tharp (2004), Pennsylvania courts no longer admit urine BAC results in DUI prosecutions.
Ideally within two weeks of your arrest. Labs typically store a second sealed vial that can be re‑analyzed; the sooner you test it, the lower the risk of degradation and the stronger your comparison evidence becomes.
Without an admissible chemical test, prosecutors may dismiss the DUI, offer a reduced charge such as reckless driving, or agree to diversion options like Accelerated Rehabilitative Disposition (ARD) for first‑time offenders.
Refusing a breath or blood test triggers an automatic driver’s‑license suspension (12–18 months) under Pennsylvania’s implied‑consent law and can be used as evidence of consciousness of guilt. While it denies prosecutors a BAC number, the civil and evidentiary penalties often outweigh the potential benefits.
After a Chester County DUI arrest, reach out to Skinner Law Firm to discuss your case. We understand the potential consequences of a guilty plea and we fight aggressively on our clients’ behalf to avoid convictions and minimize any negative impact. With a record of helping clients show the faults in improper BAC testing, we may be able to help you secure a dismissal, reduced charges, or another favorable result to your DUI charges.
For more in-depth advice, call (610) 436-1410 or contact us online to set up a free initial consultation.
Michael J. Skinner, the founder of Skinner Law Firm LLC, is a former prosecutor with the Chester County District Attorney’s Office.
