Can police tell if drivers are stoned? With new ruling in N.J., the debate continues.

Can trained police officers reliably determine if drugs have made someone unfit to drive?

The answer to that question remains in legal limbo in New Jersey, where the state Supreme Court held off on deciding a long-awaited DUI case Friday.

But in referring the matter for further review, the court announced new, stricter rules for criminal court judges to determine when experts can testify about any branch of science or medicine.

Until now, judges could allow testimony about a scientific theory or methodology upon determining that it was “generally accepted” by the field in question. From now on, judges must evaluate whether the methodology is reliable, by asking questions about its accuracy and how it was tested.

It is not yet clear what the tougher standard will mean for the trained police at the center of the New Jersey case, called drug recognition experts.

Police are trained to use a 12-step method to determine if a motorist is impaired due to drugs, a process that includes assessing the suspect’s muscle tone, pulse, and eye movements, among other vital signs.

While the method can work for some drugs, scientists say it is not reliable for marijuana. That’s because the chemical components of marijuana can be detected in the body for days after it is consumed, and long after any drug-related impairment has worn off. So if a motorist appears impaired, it may be due to another cause, such as a medical condition.

[Read more at The Philadelphia Inquirer]