The Consensus Opinion here is Flat Wrong. (Score 1)

The amount of ignorance here is simply **astounding**. The breath alcohol measurement instrument is not a witness. The instrument is a thoroughly tested and vetted measurement device. Do you have the right to subpoena the source code to the radar gun that busted you? Do you have the right so subpoena the source code to the gas chromatograph that shows you were doping? If a MRI system from Siemens shows a bullet within a corpse used as evidence in your murder case, can you subpoena Siemens for their source code? These sorts of challenges are called FRIVOLOUS FISHING EXPIDITIONS. The testimony of hired guns spewing weak opinion as fact about programming metholodgies, interrupt driven event handlers, and whatever other techno babble they can come up with is typically meaningless, prejudicial to jurors and more often than not amounts to made up versions reality. If the program that performs this analysis runs under Mac OS 10, do you have the right to subpoena the source code for the Apple Operating system go before a jury and make claims that an alleged security flaw you found render the breath result invalid? Hogwash. A chemical reaction within a fuel cell produces a voltage. Integrate the voltage over time produced by a fuel cell converting a sample of ethanol to electricity and the integrand is proportional to the volume of ethanol that existed in the fixed sample. The relationship between blood alcohol content and breath alcohol content is based upon the scientific method. The linearity of the measurement device is by design and the result CAN be affected by temperature, pressure, smoke, certain interferants, radio frequency interference, etc., etc. etc. That's why the device, its testing procedures and environment are carefully set up, monitored and documented, its calibration regularly checked and the instrument gets the hell tested out of it across a huge range of conditions to prove its immunity within acceptable operating conditions. Expert testimony can fill in details of the methodologies, technologies and algorithms implemented. But if the instrument is a "witness" then the defense's right to have the source code for the measurement instrument is as strong as their right to know the synaptic bond strengths of every neuron within the brain of the officer that witnessed and testified that the defendant drove into oncoming traffic. There is no such right.