5700 Granite Pkwy #200 Plano, TX 75024
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Breath Test Defense

The majority of DWI cases in Texas involve a breath test reading. For law enforcement, breath tests are cheap and easy to administer. The breath test machines, however, are not necessarily accurate and reliable.

DWI Breath Test Cases in Plano

If you failed a breath test and are facing DWI charges as a result, do not lose hope. At Law Offices of Richard C. McConathy, we take on breath tests and seek to expose their flaws. Call us today at (972) 805-8855 to set up a free consultation.

We represent clients throughout Collin County, including Plano, Frisco, Allen, McKinney and Murphy.

Information on Fighting DWI Breath Test Results

Assumptions in Breath Test Cases

The first problem with breath test machines is that it makes many assumptions including:

  1. your temperature is normal when every degree of body temperature above normal will cause a 7% artificial increase in the breath test reading;
  2. your “partition ration” is 1:2100 when it actually varies from 1:1500 to 1:3400.
  3. your blood alcohol level has already peaked because if the breath test is conducted before the peak the reading can be up to 50% higher than your blood alcohol concentration;
  4. it is measuring alcohol when other solvents such as acetone and ketones are causing an inflated reading;
  5. it measuring alcohol from the deep lungs when the alcohol might be coming from the stomach after a burp or belch which causes an inflated reading;
  6. it measures alcohol from the deep lungs when it might be measuring residual alcohol trapped in dental work or dentures which cause an inflated reading.

These problems and many others are well documented and even included in police training manuals. Defense attorneys are able to use all of these problems in court to show that just because the machine showed a breath test reading over .08 does not mean that the reading was accurate or reliable.

Errors in Breath Test Devices

Additionally, human error in operating or maintaining the machine is also a common problem. The defense attorney can move to suppress the results if the machine was not working properly or if the procedures set out to inspect, clean and calibrate the machine were not followed properly.

Other common defenses presented at trial include an allegation that radio frequency interference (RFI) inflated the reading. All radio transmitters, including cellular phones and police radios, emit radio waves. Radio transmitters interfere with the breath test machines.

Although breath test machines have metal covers, RFI still occurs. In fact, the machine alerts the operator to RFI when it occurs. Because the manufacturer of the machine keeps the source code secret - there is no way to know how much RFI must occur before the machine produces the flag. The fact that the machine alerts to some instances of RFI does not mean that the machine is alerting to all instances of RFI that are inflating readings.

Finding A Collin County DWI Attorney to Attack Breath Test Results

If you were pulled over and given a breath test on I-75, the Dallas North Tollway or any road or street in Collin County and now face charges as the result of a breath test, contact a skilled attorney at Law Offices of Richard C. McConathy today. Call (972) 805-8855 to set up a free consultation.


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DWI Blood Test Case + Prescription Meds
DWI Breath Test Case, Result Of .224
DWI Breath Test Refusal
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DWI, Open Container
2nd DWI, Breath Test Refusal
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5700 Granite Pkwy #200
Plano, TX 75024

405 SH 121 Bypass #A250
Lewisville, TX 75067

Principal location
15110 Dallas Pkwy #400
Dallas, TX 75248


Office: (972) 805-8855

Fax: (972) 239-0398