In recent months, Vermont authorities have ramped up the hiring of drug recognition experts to help determine if a driver is impaired on something other than alcohol. But, defense lawyers and the ACLU are among those who continue to criticize the move, saying DREs are not scientifically reliable.

St. Johnsbury-based attorney David Sleigh said when it comes to the credibility of the drug recognition protocol, the margin for human error is just too much to trust.

"The state's trying to take subjective observations and make them look like scientific results, and they're not," Sleigh said.

WCAX wanted to see what the standardized, voluntary 12-step DRE evaluation looks like. In a demonstration, Dan Goodman of AAA played the role of an impaired driver and Vermont State Police Trooper Jay Riggen conducted the evaluation.

It starts as a normal traffic stop. The officer administers a breath alcohol concentration test. If the test doesn't explain the driver's impaired behavior, the officer requests a DRE evaluation. The driver can refuse the evaluation, but that evidence may be used against them in court.

The officer asks about the driver's behavior, appearance, and driving. They observe the driver's eyes, looking for dilated pupils. They also check balance, vital signs, and muscle tone because certain drugs make muscles rigid while others can make them flaccid. The trooper also checks for injection sites.

Then the trooper goes over all the findings with the driver. The entire process can take anywhere between two to four hours. Some of it is done at the police station.

"Together, all those facts and circumstances -- we can articulate that person has some impairment," said Vermont State Police Lt. John Flannigan, the state's DRE coordinator.

Then, if the driver gives permission, police can take a blood sample for testing, but Flannigan says the results of that test don't always support the DRE's opinion,"because there are limitations with labs and laboratory equipment, and they don't test for every substance that could potentially impair an individual," he said.

Flannigan also said a medical condition could explain someone's erratic behavior. That discrepancy is why attorneys like Sleigh think the DRE program needs a lot more work to be considered credible.

"In order to scrutinize this program, the state should make a database of every DRE evaluation, particularly those that lead to subsequent blood testing, and compare the DREs conclusions with the results of the blood test," Sleigh said.

Ultimately, police just want people to know -- driving is hard enough without alcohol and drugs in your system, so if you feel impaired for any reason, get out from behind the wheel, and do your part to keep Vermont roads safe.