Inadequacies of Saliva Testing for Cannabis

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Joined: Sat Jun 11, 2011 4:31 pm

Inadequacies of Saliva Testing for Cannabis

Postby justiceintruth » Sat Jun 11, 2011 6:54 pm

It might sound hard to believe, but the saliva testing technology and protocols used in Victoria to prosecute people have some serious flaws.
In fact the manufacturer/s have actually known about, but failed to highlight these flaws (not surprisingly) in their sale pitch/s to the government (again not something new - gov. jumping onboard with unproven technologies), even though at least some of their published research (eg. by Cozart) and plenty of other independent research has clearly shown these flaws exist.

I'll now get to my point/s:

:idea: Saliva testing is very unreliable in adequately detecting cannabis use/intoxication.

This is because the active principle of cannabis THC is highly lipophilic (dissolves in fats, not in based water mixtures like saliva) meaning it doesn't (unlike alcohol) freely diffuse from the blood into the saliva. This also means saliva levels also do not give a meaningful indication of the level of intoxication (unlike blood conc's). The evidence for this abounds in the journal literature so I won't quote the myriad of recent research articles available, but I will quote an article cited elsewhere on this forum under the topic 'How Long after you smoke before you can drive?':

"Although THC is found in Saliva (or more correctly, oral fluid), levels are very low and there are often difficulties in recovery from collection pads. Essentially, THC comes from debris within the oral cavity after smoking, rather than diffusion from plasma."(1)

I have also read at least one published research paper by Cozart (which I don't have handy right know, but could find) which showed how even persons tested only minutes after smoking cannabis can test negative using this technology, essentially if their saliva is rinsed clean by liquid consumption or further saliva flow.

A brand new paper in print, examining saliva THC levels after oral THC consumption also sheds light on the situation:

Anal.Bioanal.Chem. 2011 Jun 3[Epub ahead of print]
Cannabinoids and metabolites in expectorated oral fluid after 8 days of controlled around-the-clock oral THC administration.

"Expectorated Oral Fluid specimens (n=360) were obtained from 10 adult daily cannabis smokers before, during and after 37 20-mg oral THC doses over 9 days to characterize cannabinoid disposition in this matrix."
..."THC was detected in only 13.8% of specimens"
..."A total of 2.5 and 3.5% of specimens were THC-positive at the recommended Substance Abuse and Mental Health Services Administration (2 ng/ml) and Driving Under the Influence of Drugs, Alcohol and Medicines (DRUID)(1 ng/ml) confirmation cutoffs, respectively. THC is currently the only analyte for monitoring cannabis exposure in OF; however, these data indicate chronic therapeutic oral THC administration and illicit oral THC use are unlikely to be identified with current guidelines. Measurement of THCCOOH may improve the detection and interpretation of OF cannabinoid tests and minimize the possibility of OF contamination from passive inhalation of cannabis smoke."

This again is clearly showing again the flaws in oral fluid testing for cannabis use - what-ever the technology involved!
The inadequacy of saliva testing for cannabis is obvious if cut-offs of as low as 1 ng/ml (it would be nice to know the Victorian cut-offs) still FAIL to detect the THC and relates to its physical properties of THC mentioned above, rather than a failure of the current technology used (meaning an alternative source of sample would be desirable for more accurate testing, rather than an improvement of the accuracy or resolution of the current technology)

:idea: Saliva testing for cannabis use persecutes innocent parties.

This notion is probably even more contentious than the last, but non-the-less true.
Again if one looks closely at the available published data it is clear that it is indeed very possible to test positive to an oral test for cannabis WITHOUT having purposefully having inhaled cannabis smoke. The various law enforcement bodies in question don't deny this, but rather counter with the suggestion that a subsequent blood test will/does prove whether or not the person had indeed purposefully smoked cannabis by indicating either sufficiently high THC levels and/or showing metabolism (as was even suggested in the above quote from a new research paper).
Yet these ideas (whether accepted by ignorant law enforcement or excessively optimistic researchers) are still blatently
wrong, since by definition (from available research) if cannabis smoke has entered a persons mouth even unintentionally in a sufficient concentration to reach or pass a cut-off of 1 or 2 ng/ml it will also have been in sufficient concentration to enter that persons blood (even via the mouth and throat if it didn't reach the lungs - yep, Bill Clinton never had to inhale to get high!) and hence produce a positive subsequent blood test.

This means that a person walking down the street past another person smoking pot may get into their car drive down the road, test positive roadside (via saliva and then blood) to cannabis, then go on to be prosecuted (remember it's almost always easier or advised to plead guilty in such cases too) and yet never having intentionally consumed it!

Quoting from :
"The blood or urine is then tested for drugs and if drugs capable of impairing the driver are found the driver is prosecuted. On a strict reading of the legislation it is not necessary to prove that the drugs impaired the driver's ability to control a motor vehicle."

In other words if it's demonstrated that a person in Victoria was driving prior to a positive test to any blood concentration of THC (tetrahydrocannabinol) then that person is automatically guilty of an offense, even if that concentration is below a known intoxicating level (a situation likely if a person innocently/unintentionally inhaled cannabis smoke).

Now I'll give another example of researchers excess optimism (in a technologies ability to deliver a desired result), which is likely the source for the above researchers concept that cannabinoid metabolite ratios can actually show whether or not the cannabis smoke consumption was passive or intentional!!! :

Arch Kriminol. 2010 Mar-Apr;225(3-4):90-8.
Interpretation of blood analysis data found after passive exposure to cannabis
[Article in German]

"When defendants are confronted with evidence of cannabinoids in their blood suggesting consumption of cannabis they sometimes argue that this could only be due to a passive exposure. The small number of controlled studies available showed that tetrahydrocannabinol (THC), the active ingredient of cannabis, was actually found in the blood after passive exposure to cannabis smoke. The resulting blood concentrations were dependent on the applied THC doses and the size of the room in which the passive exposure occurred. However, the quantitative data indicated in the publications of the 1980s cannot be fully compared with the results of modern analytical methods. Due to the rapid distribution of THC in the body, which occurs also after passive exposure to low doses, the THC concentration in serum to be expected in a blood sample taken 1 hour after exposure is less than 1 ng/mL. For assessment of an alleged passive exposure, the metabolic THC-carboxylic acid, which is excreted more slowly, must also be taken into account. After passive exposure, similar and very low serum concentrations of THC and THC-carboxylic acid are to be expected (< 2 ng/mL), while higher blood levels suggest the deliberate consumption of a psychoactive dose."

Now I'll say it again this is nonsense which the cited journal should be ashamed to have published - the suggestion that there's some how a distinction between intentional and accidentally induced THC blood concentrations!?!

Still don't believe me, well one of the sadly few controlled studies published on the topic clearly shows (not that it really needed proving other than for legal reasons) how passive inhalation of cannabis smoke can easily achieve THC blood concentrations which could be construed/misinterpreted as indicating intentional cannabis smoke inhalation. In this study all of the subjects achieved detectable blood concentrations of THC and it was done in 1985 , before the improved analytical machines of today which can detect much lower concentrations again.

Journal of Forensic Sciences
Volume 30, Issue 4 (October 1985)
Cannabinoids in Blood and Urine after Passive Inhalation of Cannabis Smoke

"...Five healthy volunteers who had previously never used Cannabis, passively inhaled Cannabis smoke for 30 min...Tetrahydrocannabinol (THC) could be detected in the blood of all passive smokers immediately after exposure in concentrations ranging from 1.3 to 6.3 ng/mL...It is concluded that the demonstration of cannabinoids in blood or urine is no unequivocal proof of active Cannabis smoking."

and on the same topic, this research having been apparently aimed at providing a defense for a positive urine test for THCA a metabolite of THC tested for in urine:

Journal of Forensic Sciences
Volume 42, Issue 2 (March 1997)
An indoor air quality—pharmacokinetic simulation of passive inhalation of marijuana smoke and the resultant buildup of 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid in urine

In military courts of law, the good soldier defense is often used by the defendant to explain the presence of 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid in urine (hereafter referred to as THCA) above the Department of Defense (DOD) established limit of 15 ng/mL. The defense will contend the defendant unwittingly breathed side-stream marijuana smoke, thus resulting in the presence of THCA in the defendant's urine. The purpose of this work was to link an indoor air quality model (IAQ) with a pharmacokinetic (PK) model to predict a passive marijuana smoker's resultant concentration of the major urinary metabolite THCA.

So to summarize:

Evidence abounds that the current oral fluid technology used for cannabis in Victoria is flawed in both its effectiveness, since a large proportion of intoxicated users will test negative, and actual delivery of evidence of a crime (i.e. that cannabis was smoked), since a person may test positive to THC in both the saliva as well as blood tests and yet not be intoxicated nor have actually committed a crime (aside from the positive tests).

All this wouldn't worry me, since I don't smoke cannabis, except that the other day while walking down Brunswick street I walked through a cloud of cannabis smoke on my way back to my car which I was about to drive and realized I was now about to break the law!

Sadly I doubt it'll be soon before someone's brave enough to come forward after being wrongly convicted in this manner - it won't happen soon, but it will happen.


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Re: Inadequacies of Saliva Testing for Cannabis

Postby Hardy » Sun Jun 12, 2011 12:10 am

Yes, it would be better if the law created these offences above a threshold instead of being absolute.

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