How to Discredit Breathalyzer Test Evidence

Everyone knows that driving when you are under the influence of drugs or alcohol is dangerous for the driver and everyone else on the road. But DUIs still happen to good people who misjudge how much alcohol they’ve consumed. Roadside field sobriety tests help justify the police officer’s arrest of the driver, but the prosecution usually needs more to win a conviction. Breathalyzer tests are what most prosecutors rely on to prove a DUI defendant’s guilt. 


But failing a breathalyzer test does not mean an automatic DUI conviction. Breathalyzer results can be discredited and prosecutions using breath and other chemical tests can be defeated in court. At Stechschulte Nell, Attorneys at Law, here in Tampa, we think you should know that DUI cases require prosecutors to prove many details, and an error or oversight in the breathalyzer testing process can lead to a dismissal of the charge or an acquittal at trial. 


Why Prosecutors Value Breathalyzer Test Results to Get DUI Convictions 


In Florida, there are two ways for a prosecutor to prove a driver is guilty of a DUI. The law says it is illegal for a person to be driving or in actual control of a motor vehicle if  


  1. the person is under the influence of alcoholic beverages (or drugs) when affected to the extent that the person’s normal faculties are impaired [by police observation], or 
  2. the person has a blood alcohol content (BAC) of 0.08 or higher [by breath or blood testing]. 


Let’s take them one at a time. Before looking at how “DUI observation cases” are proven, let’s look at how the breathalyzer is mistakenly believed to be free of error. 


Learn More> How Does a Breathalyzer Test Work? Should You Refuse One?  


Defending a DUI Case with Breathalyzer Machine Test Evidence 


As you will see when you read how experienced defense lawyers can defend DUI cases that have no breathalyzer test evidence, prosecutors like the popular belief that breathalyzer tests can’t be successfully challenged by the defense. In fact, breathalyzer machines are highly sensitive computerized devices that can produce inaccurate results if the machine is not regularly and skillfully maintained, and then operated properly. 


In Florida, the breathalyzer model widely used  

across the state is the Breathalyzer 8000.  


Here are just a few ways in which this model breathalyzer machine’s test result can be inaccurate: 


  • incorrect administration of test by a poorly trained machine operator 
  • the machine was not regularly maintained 
  • the machine incorrectly or not calibrated 
  • breathalyzer software is outdated 
  • radiofrequency interference (RFI) 
  • source code errors (undetectable unless provided by manufacturer – copyrighted) 
  • the test subject (driver) belched, smoked, vomited, ate, or drank something within 20 minutes of providing the breath sample 
  • diabetes (natural ketones produced by the body can affect breathalyzer results) 
  • asthma medications 
  • over-the-counter cough drops with menthol, or Vicks cough drops 
  • test subjects who work around solvents (paint, lacquer, adhesives, varnish, etc.) can emit fumes that will interfere with the breathalyzer 8000 accurate breath reading 



Defending a DUI Charge Even If the Breathalyzer Test Was Correct 


What if your lawyer can’t show that the breathalyzer result is flawed? Does that mean you lose? 


No! In DUI prosecutions, the government cannot even introduce the breathalyzer machine test results until they show what the law calls a “proper foundation.” This means that the test results are only admitted into evidence if the prosecution can produce evidence that everything the police officer did up to that point was legal: 


  • Did the officer have reasonable suspicion justifying the traffic stop of the defendant? 
  • Once stopped, when the officer had contact with the driver, was there sufficient grounds to suspect the driver was under the influence of alcohol or drugs? (Officer needs details.) 
  • Did the officer administer Standardized Field Sobriety Tests (SFSTs)? 

-What SFSTs did the officer administer? 

-Did they give the instructions properly? 

-Were the lighting, road surface, and weather conditions suitable for the tests? 

-What shoes was the driver wearing? (Heels 3” or over invalidate some tests) 

-How did the officer “score” the driver’s performance? 

-Scoring specific clues is required 

-Officers often score the same clue twice with different wording 

  • Is there a bodycam or dashcam video of the driver’s SFST performance? Does it support the officer’s conclusions? 
  • Was the driver read their pre-breathalyzer rights form? 
  • Did the driver understand (language barrier, excessive ambient noise in the room, etc.) 


Defending A DUI Case Based on Only Police Observation Evidence, Without A Breathalyzer Test 


The law permits prosecutors to convict a person of DUI if there is sufficient evidence (beyond a reasonable doubt) that they were under the influence of alcohol or drugs to the extent that their normal faculties were impaired. Without a breath or blood test, the only source of evidence is the police officer whose testimony needs to persuade either a judge or jury that the driver’s “normal faculties” were impaired. 


The officer describes the defendant’s driving behavior, the manner of speaking (slurring), walking (unbalanced), responding (confused), following directions (incorrectly), along with their appearance (bloodshot watery eyes, a strong odor of alcohol, etc.). To provide the officer with some sort of “scientific” data, the officer administers two or three field sobriety tests and describes how the driver failed.  


Defending a DUI case that’s based on officer observation is a simple task for a skilled, experienced DUI defense lawyer. Each of the officer’s “observations” are descriptions of his perception and his characterizations, all of which are fairly easy to challenge as biased, even if only unconsciously, against the driver. 


Even more productive is a defense attorney’s dissection of how the officer administered the “scientific” field sobriety tests. The test result conclusions are only reliable if the officer gave the proper instructions and demonstrations before the driver performed the test, and the officer accurately scored the driver’s performance. Each of the test procedures is very technical and each deviation the officer commits renders the conclusion less accurate.  


Call the Experienced Breathalyzer Defense Lawyers for Your DUI Charge 


With years of courtroom experience defending DUI cases, and as a former DUI prosecutor, Attorney Ben Stechschulte partners with Certified Criminal Defense Attorney Amy Nell to provide the highest quality DUI defense representation in the Tampa – St. Petersburg area. 


Don’t give up on yourself. Your breathalyzer test results do not dictate how your case will be resolved. The skillful defense of every DUI client includes looking at every detail of your case to find grounds to challenge the accuracy or reliability of the prosecution’s evidence.  


Once an allegation in the evidence is questionable, favorable outcomes can be achieved either by pretrial motions to dismiss, by going to trial, or by negotiating a reduced charge for lesser sanctions and the possibility to have the case records expunged or sealed. 


For a DUI case review, call Tampa’s experienced breathalyzer defense lawyers at Stechschulte Nell; 813-280-1244.  



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