Written by attorney Joseph B Barnes III

DUI-DWI Breathalyzer and Alcotest 9510 vs Blood Test in Connecticut

Arrested for DUI and took the blood test?

the reading is over .08, Guilty? maybe NOT.

Your SUBJECT TEST refers to breathalyzer, or newer Alcotest 9510, breath test result, is an indirect estimate of your Blood Alcohol Content (BAC) at the time of the test.

While most BAC test results between 0.10% and 0.20% are within about 10 percent of the subject’s true BAC at the time of breath testing, combinations of breath test variables can result in a greater than expected difference. Even the 10% error rate acknowledged BY THE MANUFACTURER can make a big difference for your case.

Breath tests has been criticized for being subject to a variety of errors:

Machine error (1) refers to the accuracy of the breath machine’s measurement of the alcohol concentration in the captured breath sample. Some experts consider the permissible level of error for a breath test simulator (e.g. plus or minus 0.005% to 0.010%) as representative of machine error. Company, Drager, who manufactures the Alcotest 9510 acknowledges a 10%error rate:.01+/- OR MORE on the BAC Scale.

Biological error (2) refers to the error associated with the machine’s use of a fixed breath-to blood (i.e.Breath alcohol content (BrAC) vs BAC) multiplication factor of 1:2100 when indirectly estimating the BAC at the time of the breath test. This is the error due to the use of an arbitrary

multiplication factor of 2100 when the breath machine converts the measured breath alcohol level as an equivalent BAC.

Physiological error (3) refers to the overestimation of BAC when the subject’s alcohol level is rising or at a peak (i.e. when the person is still absorbing some amount of alcohol and the BAC in the blood that is going to the subject’s lungs is higher than the BAC in the rest of the body).

Chemical interference (4) refers to error due to the measurement of other chemicals similar to alcohol. Unit-of-measure: Percent by weight (w/w) BAC. Connecticut alcohol-related laws are based on percentage by weight BAC. To express a percent weight-by volume (% w/v) BrAC as a percentage by weight (% w/w), you have to divide the breath alcohol level by the specific gravity of whole blood (SpGr = 1.055).

The following is an actual letter from my office to the States' Attorney (Prosecutor) in an actual DUI case (names are changed and supporting documents omitted] :

Re: Mr. {X} [name changed to protect the Not guilty]

Docket No. [x]

DearState's Attorney {R},

I have had preliminary work done in the matter of Mr. {X} Our preliminary findings indicate that the State does not even have a prima facie case since the breath BAC by volume (.0831) must be converted to BAC by weight (0.0787), not including the other issues highlighted in the information I have enclosed herewith.

Since we are waiting to bring this to the judge based on the trial calendar and prior to making my motion and incurring additional time and expense to us both, I enclose the preliminary information on this case as a courtesy to you.

Please have your expert review same as I feel we can resolve this matter based on the undisputed facts.

Thank you for your kind attention to this matter.

Best regards,

Joseph B. Barnes

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