Breathalyzer tests are far from infallible. In fact, they can be fraught with errors if the machine used to deliver them was defective or was not calibrated correctly.

In Ventura County, 300 people are challenging their drunk driving convictions on the grounds that the hand-held breathalyzer devices used to determine their blood-alcohol content delivered erroneous results.

The device in question is the Alco-Sensor V. Ventura County purchased 128 of the hand-held devices. The manufacturer later admitted that there was a design flaw, though it wasn't clear how many of the devices were affected by the flaw.

Law enforcement officers and prosecutors like to rely on breathalyzer evidence because it is quantifiable. Field sobriety tests administered by officers at the point of arrest are notoriously subjective. Breathalyzer readings seem more straightforward and reliable in comparison.

But that's only true if the machine is working properly. If the machine is defective, or the officer did not set the machine properly, breathalyzer readings can be utterly erroneous.

In the case of the Alco-Sensor V, the manufacturer, Intoximeters Inc. in St. Louis, Missouri, initially told Ventura Country officials that breath-alcohol test results would not be affected by flaws in the device. But Intoximeters Inc. later acknowledged that flaws in the device could indeed produce erroneous results. The errors were linked, the company found, to condensed liquid contaminating the breath sample.

The bottom line is that if you've been charged with drunk driving, breathalyzer results do not necessarily make a slam-dunk case against you. Talk with us to find out more about how to fight the charges.

Source" "Defendants challenging cases linked to defective breathalyzer," Ventura County Star, 5-30-2011