Look into their eyes
Huff said one of the quickest ways to tell whether someone is under the influence of drugs is to look into their eyes.
If someone's pupils are dilated, or much larger than normal, then they might have used LSD or MDMA, also known as ecstasy.
Meanwhile, if a person's pupils are constricted, or much smaller than normal, he or she might have taken narcotic analgesics.
The eyes are important to drug recognition experts like Huff because they provide details that a person can't hide. If a person is an addict, he or she might be able to hide some of the physical effects of being high.
“The things we look for in the eyes, they can't be faked,” Huff said. “It's going to happen regardless of whether they want it to or not. People can't control their eyes and say, ‘Do not dilate.'”
Huff said it is best not to directly confront someone suspected of taking drugs.
“If you do see something that looks like a meth lab, and you confront them, the next thing that may come out is a gun,” he said. “Please, please just back out and call us.”