Cannabis plant. (Getty Images)

The state forensic science lab plans to distribute 15,000 field tests to police departments around Virginia that will help officers distinguish between hemp and marijuana plants, which can appear identical but carry very different legal implications.

“You can’t tell the difference … without some kind of quantitative testing,” said Linda Jackson, who directs the Department of Forensic Science.

The General Assembly passed legislation earlier this year allowing the production and sale of hemp for CBD, a wildly popular but largely untested component of the plant marketed as a remedy for everything from anxiety to seizures.

Since the law was enacted on an emergency basis in March, farmers have planted thousands of acres of the crop. Hemp products had already popped up in stores all over the state in preparations ranging from oils to “hemp flower,” buds of the plant that look and smell just like their contraband cousins.

But so far, law enforcement agencies have had no way to differentiate between a legal hemp product and a still-very-illegal marijuana one.

Both are cannabis plants, but the state defines hemp as having .3 percent or less THC, the intoxicating compound associated with marijuana, which can contain THC levels exceeding 17 percent.

However, lab and field tests currently in use are not capable of making that distinction in most cases – all they can do is confirm the presence or absence of any THC.

The problem is not unique to Virginia. In some states, hemp farmers shipping their crops have been charged with drug trafficking.

Closer to home, police in Fredericksburg raided a head shop selling raw cannabis flowers marketed as legal hemp/CBD products. Officials told the NBC affiliate in Washington that the products tested positive as marijuana, prompting a felony distribution charge against the owner, Kyle Traugh, which is still pending.

A spokeswoman for the department did not respond to an email seeking comment. Traugh declined to comment, citing the fact that his case is still pending, but he previously said he was assured by the product’s manufacturer that they were legal.

The forensic science department has since notified police departments that existing marijuana field and lab tests can’t differentiate between hemp and marijuana and that, going forward, their analyses would note that the concentration of THC was not determined.

The new field tests will be distributed over the next several months. The board voted Wednesday to accept $52,500 in grant funding to cover the cost, which works out to $3.50 per test.

Developed in Switzerland, the tests allow police to determine on the spot whether a plant contains higher levels of THC or higher levels of CBD.

“One would assume that if cannabis has more THC, that is the drug type of cannabis — marijuana. And if it has more CBD, that is most likely hemp, or the non-drug type of cannabis,” Jackson said. She noted the test should only be used as an investigative tool in consideration of other evidence and would not be admissible in court.

If police pursue charges, a new in-lab test will be able to determine whether the THC concentration is higher or lower than 1 percent. And, if it’s under 1 percent, a second test will be able to determine the exact amount to see if it meets the .3 percent threshold set out in the law.

Jackson said all of the tests are in the final stages of validation and testing on cases in which hemp has been raised as a defense will begin in the next several weeks.

Police say they’re glad the past few months of uncertainty will be ending soon. “We have enough to do without chasing down legal products,” said Herndon Police Chief Maggie DeBoard, who sits on the forensic science board. “But we have to be able to tell.”