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Riding high: a look at marijuana detection

By Timothy Page Feb 09 2009, 09:20 AM

With the recent passing of Massachusetts’ marijuana decriminalization referendum – which reduces the charge of possession to a mere civil fine (think parking violation) - some worry the state will see an increase of motorists driving high, an act still very much illegal. But given the difficulty of determining the degree of cannabis intoxication, it’s possible many that drive after smoking will escape police detection.

So just how do police determine if a person was driving high? Unlike the case of Michael Phelphs, police typically don’t have photographs of the suspect caught smoking to use as evidence.

Do they hold a cookie out in front of them and wait for a vicious attack? Or is there a marijuana breathalyzer out there to determine the degree of intoxication?

At the current moment, there is no technology that can immediately calculate if a person is stoned. While there are blood, urine and hair tests that can track marijuana’s main ingredient, THC, in the body, the fact remains that weed lingers around for too long a period in order for one of these tests to determine the actual intake time.

“If we pulled over someone, and we smell weed, then we have to determine if and how intoxicated this person is,” said a local Massachusetts Police Officer who asked to remain anonymous. “We would perform the basic sobriety tests because it doesn’t matter if it’s weed or booze or whatever. If something is impairing your ability to drive and we feel it is unsafe for you to be behind the wheel, then we are going to take you in.”

Unlike alcohol, which is metabolized at about an hour per beer or shot, metabolites of marijuana have been shown to stay in one’s system from anywhere between three to 90 days. While alcohol can be easily tested by such machines as breathalyzers; being under the influence of marijuana is determined by how “under the influence” you appear to be.

In Massachusetts, when it comes to your average traffic stop where marijuana is involved, it is the officer at the scene who makes the final decision of placing someone under arrest or not, based solely on judgment.

“It’s basically our word over theirs,” said a Massachusetts police officer on condition of anonymity. “That’s why they don’t just hire anybody to be police officers. We have to make a sound decision, and the person being arrested can fight it if they want to by asking to take a urine or blood test. But if we feel it’s unsafe for them to be on the road, then we take them in.”

In some cases, police rely on Drug Recognition Experts (DRE) or Drug Recognition Evaluator’s in order to determine if someone has been smoking.

“A DRE is a police officer trained to recognize impairment in drivers under the influence of drugs other than, or in addition to, alcohol,” said Lt. David Wilson of the Massachusetts State police. “By knowing the symptoms of someone under the influence of marijuana, these officers can perform [lab] tests to determine how under the influence the person is.”

DRE’s originated in the Los Angeles Police Department back in the early 1970’s after officers noticed that many of the individuals arrested for driving under the influence had very low, if any, alcohol concentrations in their bloodstream. The officers suspected that most of those arrestees were under the influence of drugs but the officers lacked the proper training and knowledge to support their claims.

In response to this concern, two LAPD sergeants collaborated with various medical doctors, research psychologists, and other medical professionals to develop a simple, standardized procedure for recognizing drug influence and impairment, thus giving birth to a multi-step protocol and the first DRE program.

With support from the National Highway Traffic and Safety Administration and various other agencies, their studies demonstrated that a properly trained DRE could successfully identify drug impairment and accurately determine the category of drugs causing such impairment. By using a standardized 12-step Drug Influence Evaluation, which includes taking notice of muscle movements, response times, pulse rates, and any other physical signs of drug use like injection sights, a trained DRE officer can determine if a suspect is or is not impaired, if the impairment is or is not drug related, and the specific category of drug present.

When opinions from DRE’s are compared to lab results of arrested individuals, the DRE’s have an 83.5 percent accuracy rate in determining the type of drug a person is on.

Of course, given its pungent or aromatic emanation – whichever your opinion - when it comes to marijuana, if a police officer can smell it, chances are they will assume intoxication. Until more advanced technology is brought into the field, like a marijuana Breathalyzer, it is basically open season in Massachusetts for potheads.

“The way the law is written right now is too open-ended,” a Boston police officer said. “When we find marijuana, we give you the $100 ticket, and if you’re being an ass and are stoned out of your mind we arrest you. Simple as that.”

For details of the DRE 12-step evaluation visit www.decp.org/experts/12steps.htm

Also Interesting:

Read More: Public Health, Legislation, Massachusetts


February 9, 2009 10:36 AM

Incorrect statement.  Marijuana is typically gone from the system after a few hours.  However, the metabolites can be detectable for several weeks because they are stored in fat cells.  Metabolites are the inert compounds left over after the THC is broken down and removed by the liver.

February 9, 2009 12:34 PM

Why isn't anyone worried about people driving under the influence of oxcycotin or vicodin? Oh yeah I forgot, because those have a warning label and people are counseled at the pharmacy. Anyway, Those impair you worse that the highest grade marijuana can. A toke off a joint is about the same as driving after taking an alka-seltzter. So what's the big deal? Cellphone texters are impaired worse than alchohol DUI's. "Drugged driving" when Marijuana is invovled makes you more defensive vs. more agressive like alchohol does. See: http://norml.org/index.cfm?Group_ID=7459 for information about a study performed on drugged drivers.

February 9, 2009 12:51 PM

Incorrect statement, Mike. The article is only stating how long it can be detected in the body, determining whether you would or would not pass a drug test, so why don't you think before telling someone that they are wrong, or just not say anything at all because how metabolites are broken down in the body is irrelevant to this story.

February 9, 2009 1:30 PM

Wrong, Emily. The article said that alcohol was metabolized quickly, while implying that cannabis was not. In fact, cannabis is metabolized more quickly than alcohol.

February 9, 2009 3:49 PM

I get what it is trying to say. someone who smokes weed is more likely to fail a drug test because weed lingers in the body longer than booze, thats why police have breathalyzers for booze because it is easily detected. Anybody can fight a cops decision to arrest them but when it comes to a weed test the chances are it will come out positive hence backing up the officers claims, so most will just accept what has happened to them.

Hardy Scott
December 14, 2010 5:58 AM

Addiction of any sort is bad. And quite unfortunately today many people are addicted to dangerous substances such as Marijuana and alcohol. Needless to say it should be taken up instantly and should try and get rid of this habit right away. The more delay we make the more it will give pain and soon a point will reach when death will be staring on the face.

January 29, 2012 1:17 PM

Dear Sir,

My question is one of practicality.  If marijuana stays in one's system, let's say, for 30 days.  And one smokes a joint on May 1st, but does not smoke anytime after that, is he at risk of being placed under arrest for a DUI if he is pulled over on May 15th?  If that is the case, and someone smokes one joint a month then, for all practical purposes, he can be pulled over at anytime and be arrested for DUI simply because the marijuana stays in his system for 30 days.  Am I correct... or does the test have degrees of intoxication that can determine that the influence of marijuana had absolutely no effect at the time of arrest?  If not, can this be legal?












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