Thursday, July 15, 2010

Two plus two equals...?

Lab technicians in a crime law servicing three Minnesota counties couldn't figure out how to calculate alcohol concentrations in urine tests, leading to test results in 111 cases that overstated alcohol concentrations by 50%. In Minnesota a breath test is included in field sobriety testing. A urine test is then conducted at the station as "confirmation" of the alcohol concentration.

The only problem was lab techs failed to multiply the urine test result by .67 which led to inflated test scores. In Minnesota, as with most states, alcohol concentration is calculated based on grams per 210 liters (g/210L) of breath, grams per 100 milligrams (g/100mL) of blood and grams per 67 milliliters (g/67mL) of urine.

In a number of cases, even when calculated correctly, the alcohol concentration still exceeded the legal limit permissible. However, since penalties for DWI in Minnesota are determined, in part, by the alcohol concentration of the driver, some motorists accepted pleas for penalties more severe than might otherwise have been offered.
"It just goes to prove there is error. Science isn't always reliable when it's conducted by people. We see other cases where juries base decisions heavily on scientific evidence." -- Virginia Murphrey, Interim Chief Public Defendant, Anoka County, MN
Interestingly enough, the police may request either a blood or urine sample to "confirm" the breath test result -- but in these cases the police chose the least reliable test possible.


Chuck Ramsay said...

Thanks for the post, Paul. I commend you getting math right, because the Minnesota crime lab still can’t.

When the lab disclosed its errors to the public, it wrote: "The alcohol concentration reported was approximately 1/3 higher than it should have been."

As you note, the error caused the tests to be reported 50% higher than they should have been, not 1/3.

I posted the lab's letter and my explanation on my blog:

I wonder if a bright fifth grader somewhere is willing to travel to Minnesota to help the lab with complex math....

Houston DWI Attorney Paul B. Kennedy, said...

Thanks for the comment, Chuck. If they can't get simple math right, it makes you wonder what else they can't do.