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Can Passive Smoking Be A defence to Drug Driving?

February 9, 2017 by in category Drug Driving, News with 0 and 0
Home > News > Drug Driving > Can Passive Smoking Be A defence to Drug Driving?

Can second-hand cannabis smoke (‘contact high’) really get you high enough to fail a drugs test?

Passive smoking and its harmful effects on your loved ones has been used by stop smoking campaigns as a reason to give up nicotine for years. However, when it comes to the potential for a ‘contact high’ induced by second-hand cannabis smoke, this is unlikely to be accepted as a valid defence to a drug drive charge. Often asked about this issue by prospective clients we have looked into whether it is scientifically possible for passive smoke to lead you to fail a drugs test.

What is the current legal stance on Cannabis?

There is zero-tolerance approach to cannabis use and driving; the current limit in England and Wales being 2µg / L of blood.

If you are found to have exceeded this limit whilst driving, you will be looking at a mandatory ban of 12 months and face an unlimited fine usually calculated by reference to 1.5 weeks’ net income. If you are also found to have committed another driving offence (say careless driving) you could be facing a high-level community order (usually 200-300 hours of unpaid work to the community) or at worst, a prison sentence of up to 6 months.

THC Content on the Rise

So, is there any truth, when people claim that they didn’t take a puff and that they were just around people who were smoking? Simply put – maybe.

Strains of cannabis are cultivated in a hydroponic (growing without soil) system and fed with a meticulously calibrated dose of synthetic nutrients to achieve its psychedelic effect for the consumer.

Over the past twenty years, the growing ‘cultivation culture’ has seen THC % levels in products rise from 2 – 3% in 1990; to 27.2 – 32.13% in 2016 for some higher-dosage products[1].

In a 2016 US survey of weekend drivers – 8.3% of road users tested positive for alcohol in their system; in contrast to 12.6% which tested positive for THC[2] (up 8.6% from 2007).

The dangers of cannabis use on the roads are well documented. Despite the expensive costs of roadside drugs tests (£18 per unit), arrest figures are rising. In Britain, out of the 5,857 roadside drug tests administered in 2016 – 3,718 tested positive for the substance[3]. This demonstrates a growing prevalence of drug use on our roads.

“Primary Highs” versus “Contact Highs”

Contact Highs refer to non-direct inhalation or consumption of cannabis (passive smoking). Being around a substantial amount of cannabis smoke to ‘get high’ is a very different proposition from how much exposure to the smoke will cause you to fail a drug test.

Your liver metabolizes THC into 11-hydroxy-THC; the psychoactive property at different rates dependant on different variables.

Therefore, just because you do not feel high doesn’t mean that you may not be over the limit. This is because cannabis can stay in your system a lot longer than the time elapsed since your last joint. Drivers frequently get caught out days after they claim to have partaken in a puff-puff-pass situation.

In famed NFL player Josh Gordon’s case – he had recorded a THC reading of 16ng/ml (1ng/ml over the NFL prescribed limit in the US) but claimed it was a result of being “around those smoking marijuana”. Is he to be believed or is Gordon simply trying to shrug his responsibility after having tested positive?

Ventilation, Ventilation, Ventilation!

Per a prominent 2015 study researchers exposed non-cannabis users to second-hand smoke (with a potency of 11.3% THC content) in a chamber for one hour whilst varying the different levels of ventilation; to simulate real life circumstances in a social setting.

It was found that this exposure to the second-hand cannabinoids under unventilated conditions did produce over the limit, detectable results in both blood and urine. There were also notable physiological responses such as increased heart rate and blood pressure.

It was also noted that the participants who did test positive had impaired motor neurone responses on basic tasks and severely impaired reaction times.

Under more ventilated conditions, even though there were less detectable cannabinoids in the blood, there were no sedative drug effects, impairments on performance or positive urine screen results.

Considering the rising number of drug driving offences, this could provide a part-explanation to the increasing statistics.

As per the available data from similar studies, it is possible for people to register over the legal limit from sitting in a poorly ventilated space with other cannabis smokers. To this effect, even though it is subjective, it is within the realms of possibilities to become high too; in cases where there are low-tolerance individuals (non-frequent smokers of cannabis) this is more likely.

This is further supported by the scientific proposition that there are two types of second-hand smoke: Mainstream smoke (exhaled from the smoker’s lungs) and side-streamed smoke (bellowing from the joint / blunt / smoking device).

Side-stream smoke can account for 85% of the smoke in a ‘hotboxed’ room (or a room with poor ventilation); exposing those around it to passive smoking.

Even though conclusive research post-2010 is a little hazy (excuse the pun) – it seems that testing positive from second-hand smoke tends to occur if the test is administered within hours of exposure to the substance. As such, if you have been exposed in any capacity to second hand smoke, it is advisable you do not operate any motorised vehicle on the roads & for non-frequent cannabis smokers to avoid small, unventilated areas such as hotboxed rooms, enclosed areas or cars.

The effects of second-hand smoke, albeit less prominent than direct inhalation, will still have an impact on reaction times and motor neurone responses if you’re driving and confronted with an emergency.

Can second-hand smoke be used as a defence or special reason?

It is the million-pound question, isn’t it?

In a report dated May 2010 from the Journal of Analytical Toxicology – researchers exposed eight volunteers to passive cannabis smoke (mainstream and side-stream smoke) before each volunteer proceeded to provide a urine and blood sample.

Further blood samples were taken 14 hours after exposure and further urine samples were taken 84 hours after exposure. Immunoassay screening techniques were employed to test for THC, THC-OH and THC-COOH using GC-MS technologies (Gas chromatography-mass spectrometry).

These results conclusively outlined that even though all participants did ingest and absorb THC – post-exposure levels were minimal and “may only lead to trace amounts of THC in serum”. This would certainly not put you over the limit for a drugs test.

Even if the court was to accept that the cannabis found in your system was due to passive smoking, this would be no defence to a drug driving charge. There is no requirement for the prosecution to prove that the drug was intentionally consumed so however it has wound up in your system is irrelevant. There may be a potential special reason to raise although this is not a defence. A special reason is an argument to persuade the court to impose a penalty below the mandatory minimum. It is potentially possible to argue like in a spiked drinks argument that any drugs in your system were there unknowingly from passive smoking. The problem with this is proving what level of drugs was from passive smoking and what was from your own drug use or proving that the amount of drug found in your blood can be attributable to passive smoking rather than actual drug use.

The court’s approach to a spiked drinks argument tends to be one of cynicism. In the absence of compelling forensic and factual evidence to support a passive smoke special reason, we expect the court to dismiss any attempt to avoid the mandatory 12 month ban applicable to drug driving.

[1] High Times, ‘The Strongest Strains on Earth’ [2016]
[2] U.S. Department of Transportation – National Highway Traffic Safety Administration, 2016
[3] The Daily Mail – The lethal epidemic drug drivers

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