Riding High: Arizona's Zero-Tolerance Stance on Pot and Driving

A couple of large mason jars full of green buds sit on the coffee table inside Tad Zaccard's west Mesa mobile home as he talks about his marijuana-DUI ticket.

"I'm a grower," admits Zaccard, a 46-year-old nutrition adviser who works for a local hospital.

As one of the state's 38,000 qualified patients, he's growing cannabis legally under Arizona's 2010 medical-marijuana law. He gets high on his own supply.

But Zaccard insists that he wasn't impaired by pot in any way when he was pulled over on the night of December 29 by a Gilbert cop working a DUI task-force patrol.

The living room of Zaccard's home is tiny, but neat. A connecting room contains thousands of vinyl records, which Zaccard spins for the classic-rock Internet radio station he operates just for fun, www.waxtraxradio.com.

On this Sunday afternoon in mid-April, Zaccard — a young grandpa who's half-Italian, half-Native American — is dressed in shorts and a black T-shirt accented with a heavy gold chain.

There's no smell of burned marijuana in the place. Zaccard seems as sober as a preacher. In his soft-spoken way, he's as full of righteousness as one, too. He's well-versed on the subject of Arizona's zero-tolerance law on driving with marijuana in the bloodstream, and he's aware that the state Supreme Court has been asked to review the law.

"I think the whole thing's criminal," he says of his arrest. "How many people does this have to happen to? I believe in this cause, and I think this needs to be addressed. It's really not right."

He relates how he was stopped just after 11 p.m. on a holiday-season Saturday night, having just finished dinner with his two adult children. Before going to bed, the unseasonably cold weather had spurred him to head out to a nearby Walgreens to buy a space heater.

Seconds after pulling out of the mobile-home park onto Main Street in his black Pontiac Sunfire, he saw the blue and red flashing lights in the rearview mirror.

Officer Eric Riley, traveling east on his motorcycle, stopped Zaccard for making a slow lane change. Zaccard disputes details of Riley's police report. He insists that he wasn't "straddling" the line between Main Street's eastbound lanes for 500 feet as he moved from the right to the left lane.

After making the stop, the cop thought the driver's speech and body movements seemed slow, his report shows. Zaccard had "extremely dilated pupils and red and watery eyes," plus a "white/green coating on his tongue," leading Riley to believe Zaccard was stoned, the report states.

A breath test showed a blood-alcohol content of zero.

Riley asked him when he'd last smoked marijuana. Zaccard told him he'd smoked one joint the day before.

Admissions like that are golden to certified drug-recognition experts, like Riley, who know that traces of marijuana can stay in the bloodstream for days or weeks.

Zaccard made a few key errors on a field-sobriety test. He couldn't walk heel-to-toe in a straight line and had trouble following instructions, Riley's report states. On the "one-leg stand" test, Zaccard "hopped" and seemed to have balance problems.

Soon enough, the Sunfire was towed, Zaccard's blood was drawn, and he was sent home with a citation.

Zaccard hadn't received a court summons, meaning the Gilbert prosecutor's office hadn't yet decided to move forward with a DUI case. His blood-test results weren't available as of press time.

Yet the prosecution, in theory, probably has an airtight case. Zaccard is a regular user of marijuana. So it's all but certain he'll fail the blood test. His medical-marijuana card won't help him if Gilbert presses the case, because of the technicality that doctors recommend, but not prescribe, marijuana.

Even if a person admits to smoking a little pot before driving, it's still reasonable to ask whether his or her level of impairment is comparable to a .08 BAC, the point at which a driver is considered legally drunk.

It doesn't matter under Arizona's zero-tolerance law. Technically speaking, Zaccard and everyone else with the slightest hint of pot residue in their blood — even card-holding patients — commit a legal foul every time they get behind the wheel.

Arizona is one of 15 states that has a zero-tolerance law against driving with any amount of pot in the system.

But, in keeping with the state's oddball reputation, Arizona is one of only three states that have both a zero-tolerance driving law for pot and a law legalizing the sale, possession, and use of medical marijuana.

Maricopa County Attorney Bill Montgomery — a Republican who's allied with Sheriff Joe Arpaio and is fighting to keep the drug-DUI law as is — stated during a radio show earlier this year that pot users are never legally able to drive in Arizona.

Montgomery believes that since there's no good way to determine impairment from marijuana, it's best to go the easy route — require a simple blood test that leads to lots of convictions. This gives the prosecutor's office a political boost with those who share his prohibitionist view. The right-wing county attorney has taken up the fight against the voter-approved 2010 Medical Marijuana Act where Governor Jan Brewer and state Attorney General Tom Horne, both fellow Republicans, have left off.

Following losses in court that ended Brewer and Horne's hope to thwart the intent of voters, a state-authorized medical-pot program finally has begun to bloom.

As of "4/20," a convenient reference point, 16 retail stores were doing business across Arizona, selling marijuana legally to some of the state's nearly 40,000 qualified patients. A couple of dozen more stores should be open by the state's deadline of June 8, after which there are no provisions under current state rules to license more.

That's good news for the 841,346 voters who made Arizona one of 18 states — and don't forget Washington, D.C. — that have legalized marijuana for medicinal use.

Still, a lottery held last year for 99 approved locations in Arizona hadn't produced 99 dispensaries by mid-April, because of the cloudy future of the industry. This isn't a thin haze, either, but a wall of legal smoke that makes it impossible to see what's ahead.

Montgomery is challenging the successful 2010 voter initiative in the state Court of Appeals in a case that pits him against a would-be Sun City dispensary that has been refused zoning information from the county. The heart of his argument is that federal marijuana law should trump the wishes of state voters. If Montgomery's legal fight is successful, each marijuana dispensary — representing years of dreams and hundreds of thousands, if not millions, of dollars — will blow away.

It's likely that before the state fight concludes, however, the Obama administration will make a long-awaited statement on how it intends to treat medical-pot states like Arizona, as well as Washington and Colorado, where voters last year approved legalization of marijuana for anyone 21 and over. In the days leading up to the April 20 celebrations in Colorado and elsewhere across the country, Obama's drug czar, Gil Kerlikowske, and attorney general, Eric Holder, made vague statements suggesting a compromise that might please neither prohibitionists like Montgomery nor the burgeoning billion-dollar legal-marijuana industry.

In the middle of the legal mess, the highly political Montgomery fought a trial-court decision about marijuana and driving that made perfect sense.

His opinion about Arizona's DUI-drug law, which states that it's illegal for motorists to drive with a non-prescribed drug or "its metabolite" in their blood, has been backed up on at least three occasions by the Arizona Court of Appeals. This includes a February 13 decision in the case of Arizona vs. Hrach Shilgevorkyan, whose defendant had, up to that point, won dismissal of his marijuana-DUI in two lower courts.

The Valley resident and his lawyer, Michael Alarid, are appealing the decision to the state Supreme Court.

Hard science supports the crux of Shilgevorkyan's case. When marijuana gets processed by the body, it breaks down in the liver and kidneys into an inert molecule that's been proven non-psychoactive. This molecule, or metabolite, can show up in the bloodstream of a marijuana user for weeks after the last toke, and the state's own experts have testified that its presence alone says nothing about the potential impairment of a person at the time of a traffic stop.

Montgomery argues, and the Court of Appeals recently ruled, that when the state Legislature wrote the drug-DUI law, it intended the zero-tolerance stance to deter the use of illegal drugs.

Yet marijuana no longer is an illegal drug for many people — not under the laws of Arizona and many other states. Even the latest Court of Appeals ruling calls it an "illicit" or "proscribed" drug, though that's no longer entirely true.

The consequences of this confusing drug policy are such that whether or not the laws decriminalizing or legalizing marijuana eventually are struck down, the current situation opens the possibility for injustice to occur.

It's as though the law withdrew your privilege to drive to work Monday through Friday because, on Saturday night, you had a single glass of wine.

Worse, the zero-tolerance law, as it applies to pot clearly is misguided, if actual carnage on the road is a guide.

Statistics obtained by New Times show that despite warnings of bloodshed on the highways because of medical-marijuana laws, drivers with cannabis in their systems make up less than 1 percent of suspected impaired drivers believed to have caused fatal and injury crashes.

For a host of reasons, the state's total ban on marijuana in the blood of drivers has been rendered obsolete.

Like Tad Zaccard, East Valley resident Hrach Shilgevorkyan insists he wasn't high or impaired in the slightest when he was pulled over.

At least, that's what he says through his Phoenix lawyer, Michael Alarid. Shilgevorkyan, on the advice of his lawyer, wouldn't speak with New Times for this article.

Shilgevorkyan, a 28-year-old restaurateur, was pulled over in December 2010 by a state highway patrolman who accused him of speeding and making an unsafe lane change. The trooper didn't smell any pot but thought the driver's eyes looked droopy and that his speech seemed slurred.

Also like Zaccard, Shilgevorkyan didn't ace the field-sobriety test and admitted he'd smoked marijuana the day before.

Accusing the 28-year-old of being stoned while driving, the Department of Public Safety officer took him to a station and had his blood drawn about 90 minutes after the stop. He wrote Shilgevorkyan two tickets — one for driving while impaired and one for driving under the influence of a drug.

The blood test ultimately would reveal a relatively tiny amount of an inactive metabolite of marijuana called carboxy-THC.

Quick pot-metabolism primer: You've probably heard of THC (delta 9-tetrahydrocannabinol), the psychoactive drug in marijuana that gets people high.

When ingested, THC flows through the bloodstream into the brain, the eyes, and other places that are rich with cannabinoid receptors. This "active" THC causes changes in perception, a feeling of well-being, and sometimes paranoia.

Research by the National Institute for Drug Abuse claims that active THC can be present at some levels in the blood of extreme stoners for up to three weeks, and that a corresponding negative effect on motor skills and thinking — both of which are rather important when driving — can be measured for up to that long, too.

Lots of different chemicals are produced when the body metabolizes THC. Arizona crime labs usually test for three molecules when examining blood for evidence of marijuana use: THC, its primary metabolite, hydroxy-THC, and the inactive metabolite carboxy-THC.

No one can predict the level at which any particular driver is too impaired by active THC.

Although 5 nanograms per milliliter is the legal cannabis threshold for drivers in Washington, a spokesman for the Washington State Patrol says it's still unclear whether that's the "right number" for determining whether a driver is impaired.

"We're studying the studies," says Robert Calkin, Washington State Patrol spokesman. "At this point, we have not reached a conclusion either way."

But one distinction needs to be emphasized: Washington's threshold applies only to active THC — not to the metabolite hydroxy-THC and certainly not to the inert secondary metabolite, carboxy-THC.

No question exists about whether carboxy-THC can impair a driver: It can't.

Nor does the amount of carboxy-THC in the blood or urine at any given time reveal how much active THC was in the body at the time of a traffic stop.

Though the DPS crime lab tested Shilgevorkyan's blood for active THC, the test revealed only the presence of 8 nanograms per milliliter of carboxy-THC.

With no strong evidence of impairment from Shilgevorkyan's driving behavior, the condition of his eyes, or his minor failings in the field-sobriety test, county prosecutor Sean Coll moved to dismiss the first charge of driving while impaired. The state's zero-tolerance law allowed the state to continue pressing the charge of driving with an illegal drug in the bloodstream.

With Alarid's help, Shilgevorkyan moved to dismiss the case based on the idea that the DUI-drug law refers to the drug and "its metabolite," which clearly is in the singular form. The state tested for two metabolites, though — hydroxy and carboxy. Therefore, Alarid argued, the test for the second metabolite was no good. An Arcadia Biltmore Justice Court judge agreed and dismissed the case.

Bill Montgomery's office appealed the ruling to county Superior Court, where Commissioner Myra Harris found Alarid's arguments compelling enough to reject the state's appeal. Harris noted that previous court rulings on state statutes allow for singular words to be considered plural — and plural to be considered singular — if the interpretation advances the intent of lawmakers.

In her ruling on May 12, 2012, Harris noted that it was possible under the state's current scheme for sober drivers to be cited for DUI, convicted, and punished with up to 10 days in jail and a $1,000 fine. Surely, convicting unimpaired drivers for impaired driving couldn't have been the Legislature's intention, Harris reasoned.

Her ruling, made before the historic legalization votes in Colorado and Washington, tried to take a fair look at how the zero-tolerance law for drivers fits in with the current marijuana policy in Arizona and other states. She concluded that it didn't.

"Other states have decriminalized marijuana use or substantially lowered the classification to a petty offense," Harris wrote. "Residents of these states . . . are likely to travel to Arizona. It would be irrational for Arizona to prosecute a defendant for an act that might have occurred outside of Arizona several weeks earlier."

Attorney Alarid points out that he didn't even need to bring in expert testimony for the Superior Court appeal, because the state's expert conceded that carboxy-THC can't impair anyone — and can't be used to determine impairment.

The state's position that it's okay to prosecute people for a pot-DUI because of the presence of carboxy-THC is "absurd," Alarid declares.

In February, though, the Court of Appeals sided with Montgomery and upheld these prosecutions. Like Harris, the appellate justices were forced to try to read the minds of previous legislators and determine their intent in forging the DUI-drug law. The justices concluded that "its metabolite" could be considered plural because lawmakers must have wanted to deter drivers from having any "illicit" drug in their systems.

Alarid's appeal to the state State Supreme Court argues that the appellate justices erred by considering the "outdated premise" that marijuana is an illicit drug.

Not only does Alarid hold out hope for his client's case, but he says this is the best chance for the state to get rid of the bad law. He believes that individual lawmakers would be too afraid of getting labeled soft on crime to ever push for leniency for pot-using drivers.

Even if doing so would be rational.

On the night of February 20, 2012, Tempe resident Michael Poshka, 30, allegedly slammed his Jeep Cherokee into a woman walking near Eighth Avenue and Stapley Drive in Mesa, then drove away and left her to die beside the road.

After a witness called in the collision, Poshka quickly was stopped in the area by a patrol officer. He and the Jeep reeked of pot, and Poshka "was having a difficult time standing up and was speaking very slow," a police report states. Two officers also noticed a faint smell of booze on Poshka's breath; he denied drinking or hitting anyone. He refused a breath test, wouldn't allow officers to look into his eyes, and refused a field-sobriety test. He admitted to smoking pot three days earlier.

A crime-lab report revealed that Poshka had 8.9 ng/ml of active THC in his blood just after the crash (and, if you're curious, 105 ng/ml of the inactive carboxy-THC).

By the numbers, he was too high to drive in any state. But the test also showed a BAC of .147, slightly below the state's "extreme DUI" limit of .15. Even without the pot, Poshka's BAC suggests he was still a serious risk to other drivers.

Had he stuck to pot only he probably wouldn't have crashed at all.

Despite the fact that marijuana is the second-most-used mind-altering substance behind alcohol in the country, pot trails alcohol and less commonly abused drugs when it comes to crashes, a New Times review of records shows. Compared to crashes believed to have been caused by booze, pot is nowhere close to being in the same league.

Statistics compiled by the Arizona Department of Transportation each year show that alcohol impairment is believed by police to be responsible for five to 10 times the number of fatal and injury crashes statewide as all other illegally used drugs combined.

For instance, in 2011, ADOT stats show that more than 16 percent of drivers believed responsible in fatal crashes had been drinking, while 3.5 percent had been under the influence of drugs (but not drinking).

Marijuana, obviously, makes up a fraction of the latter category.

State officials were unable to provide specific pot stats. To determine the number, New Times asked several Valley police agencies to provide the drug and alcohol test results in fatal and injury crashes from 2012 that involved a suspected impaired driver. Only Scottsdale and Chandler provided all the information; Phoenix gave up most of the info but did not provide all the alcohol-impairment test results.

Chandler reported blood-test data for 48 crashes involving impaired drivers who hurt or killed people in 2012. Nearly every one was attributed to alcohol. One driver was impaired by meth. No cannabis was detected in any of the drivers.

In Scottsdale, blood-test results were available in 100 of 117 serious crashes involving suspected impaired drivers from November 1, 2011 to December 31, 2012. (The other 17 crashes didn't become police investigations for various reasons, police say.)

Only one of the 100 cases involved a driver who tested positive for just pot. By comparison, three of the Scottsdale cases involved suspected impaired drivers who didn't test positive for any drug or alcohol.

Four other drivers came up dirty for pot — but also tested positive for booze, (two cases), Xanax (one case), and cocaine (one case).

Last year, Phoenix had no cases of injury or fatal crashes believed caused by people high on nothing but marijuana.

Pot was, however, involved in some of Phoenix's most serious crashes in 2012. Drivers who are drunk or high on other drugs sometimes also may have pot in their bloodstreams. The combined effect of several substances seems to have a horrendous consequence for some drivers. But figuring out whether pot contributed to the drivers' impairment often is like asking which snowflake caused the avalanche.

For instance, one driver suspected of causing a fatal crash in Phoenix tested positive for THC — but also had a .021 BAC and four different kinds of prescription sedatives. In another THC-positive case, the driver also was legally drunk and on cocaine.

In addition to crash stats, New Times reviewed all the DUI-drug cases involving marijuana in 2012. All told, Phoenix handed out 6,118 citations for DUI last year. Here's the breakdown, according to the Phoenix PD:

• 300 of the cases involved drugs and no alcohol.

• 111 of the 300 drug cases involved marijuana.

• 58 of the 111 involved just marijuana, while 53 people tested positive for pot, alcohol, and other substances.

• In 336 of the alcohol DUIs, drivers also tested positive for pot and/or other drugs.

Out of 15 fatal crashes involving suspected impaired drivers from November 2011 to November 2012, Phoenix police records show: Six were impaired by alcohol only; three had used booze, pot, and other drugs all at once; one tested positive for pot and meth; one was positive for alcohol and sedatives; and four tested positive for neither drugs nor alcohol, with no drug analysis having been performed on one of the four.

Information on fatalities in which the suspected impaired driver was killed were not obtained by New Times, though police predict that autopsy toxicology reports would reveal several more cases of drivers with alcohol, drugs, or pot in their blood.

An unknown number of alcohol-and-pot cases don't show up in the data, police say, because when a driver is found to be clearly drunk, police don't opt for a drug test, which costs more money.

Still, police in jurisdictions contacted by New Times say they always request either an alcohol or drug test for suspected impaired drivers. Phoenix, Scottsdale, and Chandler records show that, at least last year, police suspected relatively few drivers involved in crashes of being high.

"I'm not going to complain," says Detective Kemp Layden, supervisor of the Phoenix police Drug Recognition Expert program. "Obviously, alcohol is more of a problem."

County Attorney Montgomery declined to provide any evidence that his office has prosecuted a cannabis-only driver for causing a fatal or injury crash.

Records of pot-DUIs and crashes do suggest that marijuana can impair drivers. In the DUI cases, police reported pulling over drivers for weaving, speeding, driving too slowly, driving without headlights on, or other potential signs of impairment.

Blood tests revealed only the carboxy metabolite in some of the suspected marijuana-DUI drivers (precise THC measurements weren't available in all the cases). It's impossible to say for sure in these cases whether the investigating officer was incorrect about suspected impairment, the test was only for carboxy-THC and not active THC, or that levels of active THC and hydroxy metabolite (which has psychoactive properties) had dissipated by the time of the blood draw.

Layden denies that he or other Phoenix officers abuse the zero-tolerance law, which he says can't be applied without an accompanying suspicion of impairment.

In other words, Phoenix cops wouldn't pull over actress Amanda Bynes and cite her under the zero-tolerance law just because they'd seen a recent paparazzi picture of Bynes smoking pot in her car.

Still, Layden admits the obvious: Police can be mistaken about a driver's impairment. By his rough estimate, 90 percent of people who do poorly on field-sobriety tests are impaired.

But that leaves plenty of unimpaired people failing to count off 30 seconds while balancing on one leg. Some innocent drivers may have used marijuana a week before getting pulled over — in which case they still could be convicted.

Between the potential for overzealous enforcement, the scientific uncertainty about how marijuana affects driving, and the reality that pot is legal or almost legal for millions of Americans, enforcement of Arizona's zero-tolerance law is a ripe environment for injustice.

In the past two decades, studies have shown that the THC in marijuana may cause an elevated crash risk for motorists, especially in increased dosages.

Problem is, no one knows precisely why THC affects driving — or what levels of THC in the blood lead to impaired driving. And relatively few studies have been conducted on real-world crash data: State officials and police said no one ever had examined the actual blood-test data on drivers involved in Valley crashes before this year's request from New Times.

According to a widely reported study published in the British Medical Journal last year, "acute cannabis consumption nearly doubles the risk of a collision resulting in serious injury or death."

Sounds serious. But if it's true that pot is a major risk for drivers, and if it's also true that — as surveys show — as many as 15 million Americans may be regular marijuana users, why are there so few pot-caused accidents in the Phoenix area?

Police and other experts offer theories.

People often go out for drinks, which involves driving, points out Scottsdale police Sergeant Mark Clark. But with no marijuana bars (Phoenix's Vapor Lounge for medical-pot patients is an exception), people under the influence of pot may have less reason to get behind the wheel.

But there's also the simple fact that marijuana doesn't get users as wasted as alcohol or pills.

A chart seen by college students across the country shows a continuum of alcohol effects based on BAC: At three times the legal limit of alcohol, most people struggle to stay conscious. At five times the legal limit, death is a very real possibility for alcohol users.

No such continuum exists for pot, which is less toxic than aspirin or Tylenol.

Clearly, marijuana and alcohol are two very different beasts in terms of how they act on the body and affect the brain. This was shown in dramatic fashion during a 1993 on-road study of marijuana conducted by the National Highway Traffic Safety Administration, which concluded that it wasn't possible to predict driving impairment by the level of THC in the blood.

The blood of drivers "showing substantial impairment in these studies contained both high and low THC concentrations; and drivers with high plasma concentrations showed substantial, but also no impairment, and even some improvement."

Later studies lean toward the idea that concentrations in the neighborhood of 2 to 5 nanograms per milliliter may be predictors of impairment, though not always. Still, that some drivers with high THC concentrations showed no impairment or even "improvement" in driving is remarkable. A similar result for any study involving alcohol and driving would be unimaginable.

At the same time, the revelation that some drivers with low THC concentrations can show "substantial impairment" should raise concern among any marijuana user who doesn't want to hurt someone in a crash.

Novice users may be at particular risk of that.

For example, a 16-year-old crashed into one car, fled, then hit a parked car last year. He admitted to Phoenix police that he felt "light-headed" after smoking pot and knew he shouldn't have been driving. A blood test showed he had 2 nanograms per milliliter of active THC in his body. If he'd been stopped in Nevada, he would've been at the legal limit for that state, but the teen wouldn't have been considered too high to drive in Washington state.

Compare that to the findings of a 2009 study of heavy marijuana users funded by the National Institute on Drug Abuse. The study took 25 long-term heavy users and put them on the wagon for a week in a secure clinic where they could be examined (and where they couldn't toke up). NIDA researcher Marilyn Huestis, who participated in the study, tells New Times that some of these heavy users reported smoking up to 60 joints a day before they abstained for science.

By day seven, six of the 25 still had measurable amounts of active THC in their systems. A user who checked in with 7 ng/ml in his blood still had 3 ng/ml in his system on the last day. The residual THC still affects the brain and, based on other studies, could cause impairment for driving, Huestis says.

When ingested, the active ingredient in pot finds common receptors in the brain that are involved in "critical functions . . . control of movement, divided attention, critical tracking, staying in the lane," she says.

One thing the study didn't research, though, was users' actual driving histories. Asked whether her research made her comfortable enough to predict the percentage of suspected cannabis-caused crashes in Phoenix last year, Huestis declined to throw out numbers.

Daniel Rees, an economics professor at the University of Colorado-Denver, says his research shows that traffic fatalities have declined in states that have legalized marijuana for medical use and that the decline appears to be related to the new marijuana laws. Rees says his paper on the study will be published this month in the Journal of Law and Economics.

His theory is that enough people in the pro-pot states have substituted marijuana for alcohol use to make a difference in the crash trends. Even if the study from the British Medical Journal is correct about the crash risk for drivers doubling after pot use, Rees pointed to a 2004 study that showed drivers with a .08 BAC were 10 times more likely not just to be in a crash, but to cause one.

"From a public-health standpoint, you want people to be driving under the influence of marijuana rather than alcohol," Rees says.

He describes the BMJ report as warning of the "worst-case scenario" and refers to other driving research that shows little to no significant crash risk for some high drivers. Rees doesn't doubt that pot affects the brain, but, he says, studies show "drivers under the influence of marijuana take fewer risks. They go slower. They put more distance between them and the driver in front of them."

For years, police have hosted events in which volunteers pound down a few drinks and then take a field sobriety test. Hilarity ensues when the subjects, who are warned not to drive, stumble around and can't find their nose with their index finger. With pot, the results aren't so predictable.

A CBS affiliate in Seattle, KIRO-TV, conducted a similar test with pot users in February, allowing volunteers to drive on a closed course and give blood to measure their THC levels. Under the watch of a Sheriff's Office drug-recognition expert, three volunteers — whose pot use ranged from occasional to heavy — smoked before driving with Cascade Driving School instructor Mike Jackson.

The sheriff's deputy and driving instructor didn't notice any problems at active THC levels that were three to five times higher than Washington's new 5ng/ml limit. With increasing dosages, however, all three made driving errors that could have gotten them into a crash or pulled over by a cop.

For Jackson, the experiment "certainly raises the question of where the legislative limit should be."

In this context, Arizona's limit of zero for THC and its metabolites clearly is too low.

If you're convicted of a marijuana-DUI in Arizona, expect the usual punishment — and then some.

Besides "a boatload of fines and fees" and at least 24 hours in jail for a first offense, motorists convicted of driving with illegal drug metabolites have their licenses suspended for a full year, instead of the typical 90 days for alcohol offenders, says Valley defense attorney Michael Munoz.

A vehicle-interlock device that detects only alcohol must be installed in the offender's car, barring a waiver following a drug-and-alcohol evaluation.

The consequences are worse for a pot-DUI than for possessing pot in Arizona, the latter usually a misdemeanor offense with no jail time and a smaller fine.

Some cities, like Tempe, don't target pot-positive drivers aggressively under the zero-tolerance law, says Robert Hubbard, Tempe city prosecutor.

"I wouldn't go out on a limb and say any amount of this stuff is a slam dunk [conviction]," Hubbard says, adding that if the levels of THC or its metabolites are low, "I'm not going to prosecute."

In Phoenix, the policy calls for prosecution even on carboxy-THC, taking full advantage of the zero-tolerance law, says assistant city prosecutor Beth Barnes.

Arizona's medical-pot law, which allows qualified patients to legally possess pot, "provides no defense" for impaired drivers, Barnes says.

The 2010 law states specifically that driving under the influence of marijuana is prohibited, but it adds that patients can't be considered under the influence "solely because of the presence of metabolites . . . that appear in insufficient concentration to cause impairment."

Barnes says her office doesn't prosecute people "solely" because of the presence of metabolites. Impairment always is alleged in these cases, she explains, and they involve at least two charges: driving while impaired and driving with drug metabolites. Driving behavior, visual clues of impairment by an officer, and performance on the field test also are taken into account.

Although state law contains an exception to the metabolites provision for people with a valid prescription for the offending drug, the medical-pot law has doctors recommending marijuana for various conditions, not prescribing it.

This provides a loophole that makes it easier for prosecutors to get convictions for doctor-recommended marijuana, but not, say, doctor-prescribed Xanax or oxycodone, which may well be worse for drivers.

Admitting to having a medical-pot card during a traffic stop might even be considered one more piece of evidence in a marijuana-DUI investigation, police tell New Times.

Munoz agrees: "These medical-marijuana cards are all DUI time bombs."

Unless the Arizona Supreme Court changes the zero-tolerance law, marijuana users in this state — even motorists passing through — should keep in mind that a conviction for DUI may be one traffic stop away.

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Ray Stern has worked as a newspaper reporter in Arizona for more than two decades. He's won numerous awards for his reporting, including the Arizona Press Club's Don Bolles Award for Investigative Journalism.