Pro Publica and The New York Times Magazine have each written about field drug testing by U.S. law enforcement agencies. The tests are undertaken with disposable kits containing chemicals. A sample is brought into contact with the chemicals and there may be a colour change, which is assessed by the officer. The essay tells the story of people against whom criminal charges regarding illegal drugs were filed, with the results of these field testing kits as the primary evidence in the prosecutions.
According to the essay, the use of the kits has various pitfalls which can lead to false positive results. For one thing, analytes which are legal to possess can produce the same colour change as illegal substances. For another, poor lighting which may be encountered in the field can distort the officer's perception of colours. Confirmation bias can occur. Also, officers may receive inadequate (or--the submitter supposes--incorrect) training in the interpretation of the colours. A former Houston police chief offered the opinion that
Officers shouldn't collect and test their own evidence, period. I don't care whether that's cocaine, blood, hair.
The essay mentions gas chromatography–mass spectroscopy (GC-MS), an instrumental method which is typically undertaken in a laboratory, as providing more reliable results. The submitter notes that portable GC-MS equipment does exist (1, 2).
Nationwide, 62 percent of forensics labs do not conduct further testing in cases in which a field drug test was used and the defendant made a guilty plea. However, the Houston crime laboratory has been doing such testing. They have found that false positives are commonplace. The district attorney's office for Harris County, Texas, which handles cases from Houston, has been informed about those test results and is undertaking "efforts to overturn wrongful convictions." In three years, about as many such convictions have been overturned in Harris County as in the rest of the United States.
Referenced stories:
(Score: 2) by Thexalon on Wednesday July 27 2016, @01:25AM
And that matters a lot:
- He's much more likely to avoid the criminal trouble I discussed earlier, solely because he's white.
- He's much more likely to be able to get a blue-collar job, for example on construction crews.
- If he somehow manages to work his way up through hard work and education, he'll be able to pretend to be someone like me who was born upper-middle-class, and be treated accordingly.
- If he really really makes good, he'll be treated as a member of the rich elite for the rest of his life.
Contrast that with a black kid who works his way up through sheer talent and hard work and education from nothing to be president of the United States, and is still treated by a lot of the country like an uppity n*****.
The only thing that stops a bad guy with a compiler is a good guy with a compiler.