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posted by martyb on Tuesday July 26 2016, @12:12PM   Printer-friendly
from the I'm-positive-there-are-false-positives dept.

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:


Original Submission

 
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  • (Score: 1, Informative) by Anonymous Coward on Tuesday July 26 2016, @04:06PM

    by Anonymous Coward on Tuesday July 26 2016, @04:06PM (#380336)

    hmm, how about a solution to the 'justice' system that would actually be helpful instead deconstructive. Off the top of my head:

    Fix obvious problems:
    arresting people based on crap drug tests? really
    asset forfeiture before a trial finding guilt? how does that even make sense

    plea bargaining system could be entirely revamped:
    Providing people with lawyers that actually have enough time to represent them (public defenders have notoriously high case loads)
    Making bond sizes meaningful but affordable to defendants without getting a loan.

    Heck, those alone would make a huge difference so I'm going to stop. But I will add that I believe that these are absolutely required by the Constitution:

    * The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures...

    * In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial...

    * Excessive bail shall not be required, nor excessive fines imposed, nor cruel and unusual punishments inflicted.

    Three amendments out of ten, without even trying, and look at number VIII, just look at it!

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  • (Score: 0) by Anonymous Coward on Tuesday July 26 2016, @04:18PM

    by Anonymous Coward on Tuesday July 26 2016, @04:18PM (#380340)

    Justice John Paul Stevens once dissented, saying that a particular asset forfeiture case constituted an excessive fine, but he was the only one.