Date-rape drag detectors flawed: drink coasters give false sense of security. (Update).

A colorful drink coaster being distributed at college campuses claims to be able to detect date-rape drugs in beverages. Not so fast, say law enforcement officials.

The coasters, manufactured by Drink Safe Technologies of Florida, read "Drink Smart, Drink Safe" and feature two test patches that turn blue at the presence of ketamine and gamma hydroxybutyrate (GHB), two drugs that render victims helpless to attack. The company claims to have sold some 50 million coasters, mostly to colleges and convenience stores, since March.

Tests performed at the Michigan State Police Crime Lab, however, failed to clearly identify GHB that had been added to a variety of beverages. "We tested red wine, cola, whiskey, and orange juice, and because three out of the four have color already, it was very hard to decipher a color change," said Anne Gierlowski, a forensic scientist at the lab. "It's a nice idea, but it's probably a nicer idea for the people selling them because they've probably made a lot of money," she told reporters.

The coaster manufacturer claims that the device is still a good prevention tool, even if it isn't completely reliable. But officials warn that there are as many as 36 different street drugs that are commonly used in date-rape attacks, Ear more than current police field tests can detect.

A recent federal report estimates that drinking is a contributing factor in as many as 70,000 sexual assaults and rapes annually.