New opportunities and challenges await New Jersey lawyers if Gov.-elect Phil Murphy makes good on his promise to fast-track legalization of recreational marijuana. If legislation permitting the sale of marijuana to persons over 21 is signed into law, lawyers best positioned to benefit from the new law will be those ready to take on a case laden with scientific issues.

Unlike the state's medical marijuana program, which is limited to people with certain health conditions, the recreational pot law will permit the sale of the drug to anyone 21 and over.

A handful of legislators has criticized Murphy's plan for swift action, calling for hearings on the potential pitfalls of legalization, its impact on minority communities and on children. Also cited by the go-slow group is a reported increase in car crashes in states that have fully legalized marijuana.

With the legalization debate set to intensify in 2018, what follows are three things lawyers should know about driving under the influence of marijuana.

1. Some evidence points to an increase in car crashes in states that make recreational marijuana legal.

Legalizing recreational marijuana use in Colorado, Oregon and Washington has resulted in collision claim rates about 3 percent higher than those states would have seen without legalization, the Highway Loss Data Institute said in a report issued in June.

Another study published in June by the American Journal of Public Health found no increase in vehicle crash fatalities in Colorado and Washington after recreational marijuana was legalized.

New Jersey insurance companies are expecting an increase in the number of crashes if the new law is enacted, due to the fact that more people may be driving while impaired, said Christine O'Brien, president of the Insurance Council of New Jersey. But it's difficult to say whether that would result in an increase in the volume of auto injury litigation, said O'Brien.

Lawyers who handle auto injury cases will need to educate themselves on injury trends in states where restrictions on marijuana have eased, and the effectiveness of the various means of measuring drivers for drug impairment, O'Brien said.

But others dispute the reported increase in crashes. State Sen. Nicholas Scutari, D-Union, the sponsor of the bill to legalize recreational marijuana, says he has met with state officials in Colorado but they have not identified any increase in accidents since that state changed its law in 2014.

“I don't see an increase in marijuana usage. I see an increase in legal usage. The misnomer about this whole thing is we're not going to increase the amount of marijuana sales, we're just going to take it out of the shadows and get rid of drug dealers,” Scutari said.

The ACLU-NJ is a leading proponent of legalizing marijuana, citing the disparate impact that drug arrests have on people of color and the opportunity to redirect funds that governments spend on drug enforcement. ACLU-NJ Executive Director Amol Sinha says the concerns about an uptick in crashes is “more of a distraction than based on fact.”

Sinha said Scutari's bill “gets us partially there,” but the ACLU would like to see the law provide automatic expungement for people with marijuana-related offenses on their records. The group also wants the state to permit people with criminal records to obtain marijuana vendor licenses, to ensure vendor license fees won't be excessive, and to permit low-income and disabled people to grow marijuana at home for personal use. Sinha also said the ACLU is seeking to have tax revenue from marijuana reinvested in social services and drug treatment for communities hard-hit by the war on drugs.

State Sen. Joseph Pennacchio, R-Morris, believes more study is needed on the traffic safety consequences of legalizing pot.

“Let's not be hasty. Let's apply common sense and reason. We are the most congested state in the country—there's a reason our [auto] insurance rates are the highest in the country,” Pennacchio said.

2. Prosecuting stoned drivers is much more complicated than prosecuting drivers impaired by alcohol.

Laws setting the blood alcohol content at 0.08 help police combat drunken driving, but a universal standard for driving while impaired by drugs has been elusive. Some states, including Colorado and Washington, have adopted a standard of five nanograms of tetrahydrocannabinol (THC) per milliliter of blood as a standard for impaired driving, but that standard has been widely criticized as a one-size-fits-all solution. Some say THC rates varies widely in users and the five-nanogram index is not a valid measurement of impairment.

New Jersey has not adopted the five-nanogram standard, and Scutari believes the key to policing impaired driving is increased training of local police to spot offenders.

At present, drivers who are impaired by marijuana are prosecuted under the Supreme Court's 2006 ruling in State v. Bealor, which upheld a conviction for driving while impaired where an officer testified that the defendant engaged in erratic driving, had slurred speech and bloodshot eyes and smelled of burnt marijuana.

Lacking a per se limit makes it harder for prosecutors to convict a marijuana-impaired driver than a driver impaired by alcohol, said Jeffrey Gold, a Cherry Hill, New Jersey, defense attorney. Gold says he thinks that lawmakers will adopt a per se limit similar to the one in Colorado if they pass the recreational marijuana legislation.

“A per se limit helps the state. What we have now is more amorphous; it's more subject to interpretation,” said Gold.

3. Defense lawyers can expect an influx of new clients charged with impaired driving if the recreational marijuana bill is passed.

Jeffrey Wolf, a criminal defense lawyer in Denver, said Colorado's legalization of marijuana brought his practice an uptick in new business from people charged with impaired driving.

Wolf says Denver police have taken an aggressive stance against impaired driving, and he says they assume a driver is under the influence of marijuana if they pull over an erratic driver and find no odor of alcohol. Making things more difficult, Wolf said, is that in Colorado such cases are tried to a jury, and jurors tend to be retired people or homemakers who are not familiar with marijuana.

Gold, the Cherry Hill defense lawyer, agrees that legalization will make more business for defense lawyers, but the difference will not be dramatic.

Jon-Henry Barr, an attorney in Clark, New Jersey, who serves as a municipal prosecutor and also handles municipal court defense, says he expects legalization of pot will bring about an uptick in impaired driving offenses and a corresponding increase in business for defense lawyers. He says marijuana-impaired drivers are stopped less frequently than drivers impaired by alcohol because drinking takes more of a toll on a driver's skills than cannabis.

Barr counts himself as a longtime proponent of legalization of marijuana.

“The status quo is a disaster. We are getting nothing positive from constantly arresting people for small amounts of marijuana possession,” Barr said.