These Machines Can Put You in Jail. Don’t Trust Them.

Any problems have “long since been resolved,” said Scott Bookman, the laboratory director at the Colorado Department of Public Health and Environment. “I am fully committed to transparency and accuracy, and we will operate with those chief principles at the forefront of everything we do.”

Mr. Friedlander, however, is skeptical.

“I don’t condone drunken driving in the least little bit, but I was trying to follow the law,” he said. “The machines that they’re using really materially affect people, and these lab bureaucrats, running their little fiefdoms, didn’t seem to give a damn if they were accurate or not.”

HOME-BREWED CHEMICALS

Colorado wasn’t the only place where human mistakes caused a cascade of problems.

When Ilmar Paegle was hired to run the breath-testing program for the Metropolitan Police Department in Washington, D.C., his first order of business was to test its Intoxilyzers. Mr. Paegle, a retired United States Park Police officer, was stunned: Every machine was generating results that were 20 percent to 40 percent too high.

That discovery, in 2010, most likely meant that years of faulty tests had convicted innocent drivers.

Mr. Paegle’s predecessor, Kelvin King, who oversaw the program for 14 years, had routinely entered incorrect data that miscalibrated the machines, according to an affidavit by Mr. Paegle and a lawsuit brought by convicted drivers.

In addition, Mr. Paegle found, the chemicals the department was using to set up the machines were so old that they had lost their potency — and, in some cases, Mr. King had brewed his own chemical solutions. (Mr. King still works for the Metropolitan Police Department. A department spokeswoman said he was unavailable for comment.)

Mr. Paegle, believing the machines hadn’t been giving reliable results for at least a decade, pulled them out of service. He alerted the city’s attorney general, whose office prosecuted drunken-driving cases.