DUI Test Results Are Not Infallible. Ms. Williams Knows How to Challenge Them.
The prosecution's DUI case often rests on two categories of evidence: chemical test results (breathalyzer or blood) and field sobriety test observations. Many people assume these results are unquestionable scientific proof. They are not. Breathalyzer machines malfunction. Blood samples get contaminated. Officers administer field sobriety tests incorrectly. When any of these things happen, the evidence against you may not be reliable — and it can be challenged.
Updated September 2026
Ms. Williams is a member of the National College for DUI Defense, an organization that provides advanced training specifically in the science behind DUI testing. With over 33 years of legal experience, she knows how breathalyzers work, how they fail, and how to expose those failures in court. That specialized knowledge is what separates an effective DUI defense from a generic one.
Challenging Breathalyzer Evidence
Breathalyzer machines measure the alcohol content in a breath sample and use that measurement to estimate blood alcohol concentration. But these machines are not perfect instruments — they require regular calibration, proper maintenance, and correct operation to produce reliable results.
Ms. Williams investigates every aspect of the breathalyzer evidence in your case, including:
Calibration and maintenance records. Illinois requires that breathalyzer machines be calibrated at regular intervals according to specific protocols. If the machine used in your case was overdue for calibration, or if maintenance records show a history of problems, the accuracy of your test result is in question. Ms. Williams subpoenas these records and examines them carefully.
Observation period violations. Before administering a breath test, the operator is required to observe you continuously for a specific period — typically 20 minutes — to ensure you do not burp, belch, vomit, or put anything in your mouth that could affect the reading. If this observation period was not properly conducted, residual mouth alcohol can produce a falsely elevated result.
Medical conditions and interfering substances. Certain medical conditions, including gastroesophageal reflux disease (GERD), diabetes, and some dietary conditions, can produce mouth alcohol or acetone that breathalyzer machines misidentify as ethanol. Certain medications, workplace chemicals, and even mouthwash can also interfere with results. Ms. Williams investigates whether any of these factors may have affected your test.
Operator certification and errors. The person administering the breathalyzer test must be properly trained and certified. If the operator made procedural errors, used the machine incorrectly, or lacked current certification, the results may be inadmissible.
Machine-specific history. Each breathalyzer unit has its own maintenance and performance history. Some units develop patterns of unreliable readings. Ms. Williams requests the complete history of the specific machine used in your test.
Challenging Blood Test Evidence
Blood tests are often presented as more reliable than breath tests, but they are subject to their own set of potential problems. Ms. Williams examines every step of the blood testing process, from the draw itself through laboratory analysis.
The blood draw must be performed by a qualified medical professional using proper antiseptic procedures. The use of an alcohol-based swab at the puncture site can contaminate the sample. The collection tubes must contain the correct preservative and anticoagulant, and they must not be expired. The chain of custody must be documented from collection through analysis — any gap in this chain raises questions about whether the sample was tampered with or confused with another.
In the laboratory, the analysis must follow established scientific protocols. Samples must be stored at proper temperatures. The laboratory equipment must be maintained and calibrated. The analyst must be qualified and must follow standard procedures. Blood samples can also undergo fermentation if improperly preserved, which produces alcohol in the sample after collection and yields a falsely elevated result.
Challenging Field Sobriety Tests
The three standardized field sobriety tests — the Horizontal Gaze Nystagmus (HGN), Walk-and-Turn, and One-Leg Stand — must be administered according to specific protocols established by the National Highway Traffic Safety Administration (NHTSA). When officers deviate from these protocols, the results become unreliable.
Ms. Williams examines the conditions under which the tests were administered. Were they conducted on a level, well-lit surface? What was the weather like? What were you wearing on your feet? Do you have any medical conditions, injuries, or disabilities that could affect your balance or coordination? Was the officer properly trained in NHTSA-standard administration and scoring?
Even under ideal conditions, field sobriety tests are not perfectly accurate. NHTSA's own research shows that the three-test battery is only about 91% accurate when properly administered — meaning nearly 1 in 10 sober people could fail. When administered improperly, the reliability drops significantly. Ms. Williams knows these statistics and uses them to challenge officer testimony about your performance.
The NCDD Advantage
Ms. Williams's membership in the National College for DUI Defense is not just a credential — it represents ongoing, advanced education in the science of DUI testing and defense. NCDD members receive training from forensic toxicologists, breath testing scientists, and leading defense attorneys on the latest developments in DUI science.
This training means Ms. Williams understands breathalyzer technology at a level that allows her to identify problems other attorneys might miss. She can read calibration logs, understand machine error codes, and cross-examine the prosecution's expert witnesses on the technical details of chemical testing. In a DUI case where the evidence comes down to test results, this specialized knowledge can make the difference.
Frequently Asked Questions: DUI Testing Challenges
Can breathalyzer results be wrong?
Yes. Breathalyzer machines are instruments that require regular calibration, proper maintenance, and correct operation. Factors including calibration errors, machine malfunction, residual mouth alcohol from burping or GERD, certain medical conditions like diabetes, operator error, and even environmental factors can produce inaccurate readings. Ms. Williams investigates all of these possibilities in every DUI case she handles.
Can field sobriety test results be challenged in court?
Absolutely. Field sobriety tests must be administered according to strict NHTSA standards, and even when administered correctly, they are not perfectly accurate. Uneven road surfaces, poor lighting, wind, rain, medical conditions, injuries, nervousness, footwear, age, and weight can all affect performance. If the officer did not follow proper procedures, the results become even less reliable.
What is the NCDD and why does it matter?
The National College for DUI Defense provides advanced training in the science of DUI defense that goes far beyond what most lawyers learn. Members study breathalyzer technology, blood testing science, field sobriety testing protocols, and forensic toxicology. Ms. Williams is one of only a small number of attorneys in Central Illinois with this credential. It means she has the specialized knowledge to challenge DUI evidence at a technical level.
Can blood test results be challenged?
Yes. Blood tests must follow strict procedures from collection through laboratory analysis. Contamination during the draw, improper use of preservatives, broken chain of custody, fermentation of the sample due to improper storage, laboratory equipment issues, and analyst errors can all compromise results. Ms. Williams examines the complete process and challenges any weaknesses she identifies.
What happens if the test evidence is thrown out?
If the court suppresses chemical test results or field sobriety test evidence, the prosecution loses key evidence. Without reliable test results, the case becomes much harder to prove beyond a reasonable doubt. This can lead to significantly reduced charges or even complete dismissal of the case. Challenging test evidence is one of the most effective defense strategies in DUI cases.
Ms. Williams challenges DUI test evidence throughout Central Illinois including Peoria County, McLean County, Tazewell County, LaSalle County, and Macon County.