Indiana doesn’t currently have a method for testing if someone is too high to drive, but a bill proposes setting the bar at 5 nanograms. (Stock photo by Ivan Balvan/Getty Images)
Marijuana, and the tetrahydrocannabinol (THC) levels that make someone feel high, is legal for recreational purposes in three of Indiana’s four neighboring states. But figuring out when someone is too high to drive has proven to be a difficult task.
“THC is probably one of the trickiest things I’ve ever tried to nail down,” shared Rep. Wendy McNamara, R-Evansville. “And two things I’m trying to do with this bill … (is) give the state of Indiana an opportunity to figure out who are impaired drivers (and) being able to do that through the qualified test that people are already using on the streets today.”
Unlike alcohol, which has decades of research indicating that 0.08 blood alcohol concentration causes impairment, THC use doesn’t have an established and roundly accepted threshold. Under current law, a Hoosier with any THC in their system could be charged for operating a motor vehicle while intoxicated without any other evidence — or a “per se” statute.
“We need a threshold of some kind,” said Michael Moore, testifying on behalf of the Public Defender’s Council. “We would prefer it to be intoxication or evidence of intoxication, but if they’re going to keep the per se statute, some threshold — like five nanograms … would have been a move in the right direction.”
House Bill 1119, by McNamara, originally would have established a threshold of five nanograms of THC in someone’s saliva as a threshold for operating a motor vehicle while intoxicated for legal purposes. But an amendment introduced by McNamara on Wednesday would allow new test results to be admissible as evidence in court — something Moore and others didn’t support.
Four House court committee members raised concerns about the new language, but ultimately only Rep. Joanna King, R-Middlebury, voted against the measure.
“I’m concerned about false positives,” King said. “… I just think this needs a longer, deeper look.”
Wanted: A test for THC impairment
Illinois, Michigan and Ohio each have legalized recreational access to marijuana while Kentucky has legalized the drug for medicinal use. Lawmakers have repeatedly opposed any efforts to regulate marijuana for either purpose.
But thousands of Hoosier cross those state borders regularly, perhaps purchasing THC in a smokeable or edible form, and potentially legally use the drug before passing back over Indiana’s borders.
They could be charged even if they aren’t impaired since the state doesn’t have a defined threshold.
McNamara told committee members she’d worked with a researcher for two years to craft the bill, which specifies that measuring THC levels in “oral fluids” must be with the Drager DrugTest 500 or SoToxa Oral Fluid Mobile Test System.
“Oral fluids” primarily refers to saliva.
The latter tests are currently available to law enforcement officers through grants from the Indiana Criminal Justice Institute and screen for other drugs like amphetamines, cocaine, opiates and benzodiazepines, according to McNamara.
She continued to say that SoToxa’s cutoff for a “positive” test was 25 milligrams of THC, while Drager had a lower threshold at 5 milligrams.
In response to committee questions, McNamara said she opted to include specific brands because of their reliability, rather than a generic term.
“If you’re going to do this, you want to make sure — from county to county — that you at least have some consistency …. Consistency is the key right now, since it’s so new,” McNamara said.
Taking the tests to court
Chris Daniels, a traffic safety resource prosecutor with the Indiana prosecuting attorneys council, said that every state wrestled with the best way to measure driver drug impairment across various drug types.
“Drug driving is an increasing problem; it’s costing more and more lives across the country and in the state,” Daniels said.
The amended bill explicitly says that law enforcement may not arrest someone “solely” because of their test result. Instead, the results are meant to be used as evidence to help a jury make a decision, McNamara said.
Daniels called it an “emerging science” and said prosecutors wouldn’t be able to “rely solely” on test results from either SoToxa or Drager. Other evidence could include a blood test, weaving on the road or failing a sobriety test.
“We would still have to prove that somebody was intoxicated under that statute — or we would still have to prove that the substance was in somebody’s blood — but having that oral fluid result come in would help bolster those results,” Daniels said.
For Moore, that wasn’t enough of a protection.
“Even though they can’t make an arrest for a positive result on these two tests, they can still charge someone. That, of course, can be brought to court (and they’d) have to answer and suffer a punishment,” Moore said. “These test results will come in without any real evidence to refute it.”
Additionally, the bill allows for state lab technicians to remotely testify in court in certain conditions, lessening the burden on the overtaxed agency. Daniels said technicians had already spent 75 hours traveling and five hours testifying in 2025.
GET THE MORNING HEADLINES.