The field test kits are used to make a preliminary determination of whether the suspect is in possession of drugs. Due to the time it takes for lab test results to come in, many law enforcement agencies use these tests as a basis to arrests suspects. The problem is that the field test kits often come back with false positive results. With the growing popularity of natural and organic products, more citizens are being arrested and charged although they do not actually possess illegal drugs. Although the suspects are eventually exonerated by official lab results, they often have to face the expense and stress of fighting criminal charges.
For more information about this phenomenon, go to:
http://www.usatoday.com/news/nation/2008-11-03-drugkits_N.htm