In the last three years, he has seen the number of drug-DUI arrests jump from 15 percent of all DUI arrests in 2008 to 23 percent in 2010. A lot of that is attributed to a rapid boom in the popularity of synthetic drugs.
The state House and Senate passed legislation this week banning a blanket of these designer drugs.
If Gov. Corbett signs the bill, Pennsylvania will become the fourth state - along with New Jersey, Florida, and Louisiana - to ban bath salts, also known as synthetic cocaine, and join more than a dozen states to ban synthetic marijuana.
Geisler hopes it would help stem the growing drug-DUI problem.
"If it's outlawed, first of all, just possessing it will be a criminal offense," Geisler said. "So the head shops selling this stuff will be in trouble, and [so will] people possessing it. So it should have a declining effect with the drug DUIs."
The new law would make synthetic pot, bath salts, and the herb salvia - made popular when pop artist Miley Cyrus' use went viral on YouTube - Schedule I narcotics.
After hearing from a Bucks County scientist who said drug dealers could have found ways around the proposed bill, lawmakers added a last-minute amendment that would help ensure that all variations of the drugs are banned.
Scientist Stephen Donovan told lawmakers people could have altered the compound and sold a "new drug" under the same name.
"Expansion of the class of drugs makes it more difficult for these entrepreneurs to come up with another uncommon use for these common chemical compounds," said State Rep. RoseMarie Swanger (R., Lebanon), who sponsored the legislation.
The American Association of Poison Control Centers said 2,700 people have been hospitalized around the country this year. Nine deaths since last year in the United States have been attributed to it.
David Hatfield, the principal of Halifax Area High School, thinks about those when he passes Fishbone Apparel, a skate shop on Jonestown Road, where the synthetic marijuana brand "barely legal" is sold.
Hatfield said he used to have a lot of respect for the place, because it provided a safe spot for teens to hang out.
"Now when I drive by I think, I wonder if they're smoking that stuff," Hatfield said.
The store's majority shareholder, Frank Gertzen, actually agrees.
"I think he's right," Gertzen said. "I think we're kind of disappointed that we resorted to selling the herbal incenses."
But Gertzen does sell them - and will until a ban becomes official - because he sees it as a minimal evil compared with other moneymaking vices.
"Recently, we just went through high school graduation, and if you look at the numbers across the state of Pennsylvania, of children involved in alcohol-related sickness or death during graduation or senior week, it's just saddening," Gertzen said.
Hatfield said he noticed that synthetic drugs came into the scene just as he felt school officials were starting to make progress in educating youths about abusing prescription drugs. But he's excited about this legislation.
"You have to fight it with education and counseling and also try to restrict availability," Hatfield said. "All those things go together. You can't just try to restrict availability without education and counseling. You want kids to be safe and make good decisions."
If it becomes illegal, Gertzen said, he'll destroy the synthetic pot on his shelves and eat the monetary loss.