The prosecution of manufacturers and distributors of synthetic drugs presents different challenges from going after typical drug dealers, law enforcement officials say.

Currently, law enforcement is in a situation similar to what it faced with drugs in the 1970s and 1980s. Then, dealers in illicit drugs such as cocaine could evade prosecution in much the same way that synthetic drug dealers are now — by slightly changing an illegal drug’s molecular structure and creating an analog.

But in 1986, Congress passed a law (PL 99-570) allowing law enforcement to charge people with manufacturing, distributing, dispensing or possessing those analogous substances.

There is not yet a similar law for synthetic drugs, however. That means that for each particular case, prosecutors must prove that the modified substance is substantially chemically similar to a scheduled illegal drug, said Timothy Heaphy, U.S. attorney for the Western District of Virginia, at the Senate Caucus on International Narcotics Control hearing in September.

In addition, there is no precedent in the synthetic drug cases — so a decision in one case that a substance is an analog doesn’t mean that substance will be considered an analog in a second case.

Caucus Chairwoman Dianne Feinstein, D-Calif., noted at the hearing that determining whether a substance is chemically similar enough to a scheduled drug to be an analog can be a subjective decision.

“Determining whether a substance meets the vague legal criteria of a ‘controlled substance analog’ really results in a ‘battle of experts’ inside the courtroom,” she said, noting that both sides will use chemistry experts to argue whether the substance meets the legal criteria.

In addition, prosecutors must prove the substance is intended for consumer consumption, Heaphy said. That can be difficult to do because the substances’ packaging is often marked with labels like “not for human consumption,” and distributors often won’t admit any knowledge that the products are meant for consumption.

Still, prosecutors recently have tried to use the analog law against synthetic drug suppliers. Heaphy notes that from 1986 to 2011, about 62 people were prosecuted for distributing controlled substance analogs — from 2011 to present, 280 people have been similarly charged.