Drug test's false positive lands college student in jail

What was supposed to be a college prank landed a student to jail, after a field drug test kit came up with a false positive.

"Really, I'm really in jail right now for powdered sugar, " John Harrington thought after it happened.  "I thought I would get a laugh and move on."

But the laughs didn't last long for Harrington. "All of sudden I was in jail eating ham sandwiches, " said Harrington.

This all started when the University of Miami student thought it would be funny to sprinkle powdered sugar on his desk during a routine dorm inspection. "As soon as my R.A.'s were.. what's this? I burst out laughing.  Oh man.. this is just powered sugar, " he explained.

But they weren't laughing. Neither were Coral Gables police when they showed up with a field drug test kit.

"When the test resulted in a positive cocaine identification, that's when they did slap the cuffs on me, " said Harrington.

He says he told them it was just sugar, but they didn't believe him.

He was arrested, charged, and spent nearly 20 hours behind bars. 

"The administration of those tests are so unreliable that it could possibly mistake cocaine for powered sugar and really I couldn't help but laugh it was just so surreal, " said Harrington.

He quickly learned what Fox 13 has been investigating for eight months.  These field drug test kits used by law enforcement to put people in jail are  often wrong.

Prosecutors offered him a plea deal, which he rejected.

He went to court a month later to face drug charges, and finally the truth was revealed.

A state crime lab determined the field drug test was wrong.

Harrington says he's lost confidence in the justice system, but saves his biggest criticism for those field drug test kits.

"It makes me really concerned as an American citizen that this pseudo science is enabling police to snatch people off the streets and throw them in jail, " said Harrington.