Sometimes science is great, sometimes it is not so great. Case in point: according to a study published yesterday, a team of researchers at Sweden’s Karolinska Institutet have developed a way to user breathalyzer-like technology to test for the presence of 12 different drugs, including cocaine, amphetamines, and yes, cannabis. As Smithsonian points out, “it’s easy to speculate that law enforcement across the U.S. (and around the world) would love to get their hands on such technology as soon as possible.”

Even worse, the researchers tested their horrible new device on subjects who had used drugs 24 hours prior to the test, meaning some false positives could turn up. Say you smoked weed yesterday, then were pulled over for totally unrelated erratic driving today–unless there’s a way to test for when the drugs were ingested, the breathalyzer may turn up a false positive.

Speaking of false positives: The test also found drugs that weren’t actually present in the subject’s system 23 percent of the time, meaning this thing probably isn’t road-ready quite yet. And it isn’t portable yet–officers would have to send data to a lab for analysis. But it’s coming.