It is one thing to have a result.  It is a whole other thing to know what to do with it.  This blog post will consider the case of positive test results and the limits of interpreting the significance of those results in various contexts.

It is estimated that as of 2009, one out of every 31 adults in the United States of America is currently incarcerated or is on probation or parole.  A typical condition of probation and parole is to that the probationer or parolee “may not ingest any drugs or alcohol”.  As marijuana (Cannabis) in certain parts of the United States is on the verge of becoming legalized or at least decriminalized, the general and ready access of citizens to Cannabis will increase.  With more and more people finding themselves on probation and/or parole, some argue this will lead to potentially higher rates of probation/parole violations perhaps due in part of positive results for Cannabis smoking.

This blog will examine the possibility of being merely present for the smoking of Cannabis and whether or not a positive result for Cannabis can occur despite taking no active role or even attempting to smoke.

What about those who are on probation/parole and are not actively smoking Cannabis but instead are around folks who are?  They may find themselves tested by blood or urine with a positive result although they have not offended the term of probation or parole that they “may not ingest any drugs or alcohol”.

What about a motorist, who is not on probation/parole and is not actively smoking Cannabis but instead is around people who are actively smoking, then is pulled over on the ride home at a checkpoint, is arrested and later tested?  This motorist may too find himself/herself with a positive blood or urine result although they have done nothing other than being merely present for the smoking of Cannabis.  [N.B., in most states being merely present for a crime without actively participating, aiding, enticing or abetting in the commission of a crime is not a violation of the law]

The typical method of testing probationers/parolees is through the use of urine testing.  A probationer/parolee is required, at random typically, to provide a sample of his/her urine for chemical analysis.  Usually an EtG screen is completed to indirectly measure if ETOH was consumed.  In addition a screen for drugs of abuse (DOA) which includes Delta-9 Tetrahydrocannabinol (THC) or carboxy Tetrahydrocannabinol is included as it is thought to be among the most abused DOAs.  When used, this assay is either radioimmunoassay (RIA) or Enzyme Multiplied Immunoassay Technique (EMIT)-based.  Rarely, but on occasion in the case of a positive screen for a DOA in the probation/parole context, the results of the screening test by RIA or EMIT are sent off for confirmatory testing by Gas Chromatography-Mass Spectrometry (GC-MS).

In the Driving Under the Influence of Drugs (DUID) context, a motorist will typically have his blood drawn and examined by GC-MS.  Some states regrettably still use urine tests to determine DUID such as Minnesota.

Oftentimes, undereducated analysts, police officers and probation and parole officers will testify or opine that passive inhalation of Cannabis will not create a positive result for RIA, EMIT or GC-MS.  They believe and are taught by other undereducated people that the passive exposure is not of sufficient character or strength where the Limit of Detection (LOD) will be exceeded.  Nothing could be further from the truth.  It is a wives’ tale that stands in stark contrast with the forensic science and analytical chemistry reality.

As LODs in analytical chemistry continue to lower as methods and instrumentation combine to create tests that are becoming increasingly sensitive, we live in the day and age where it is nearly possible to do trace analysis for DOAs in any matrix (e.g., blood, urine).

However, this issue of passive inhalation of Cannabis has been known, studied and published since at least1985.

Accroding to one publication Marland, J., Bugge, A., Skuterud, B., Steen, A., Wethe, G. H., and Kjeldsen, T., “Cannabinoids in Blood and Urine alter Passive Inhalation of Cannabis Smoke,” Journal of Forensic Sciences, JFSCA, Vol. 30, No.4, Oct. 1985, pp. 997-1002, the main conclusion of this 25 year old study is that the demonstration of canabinoids in blood or urine is not unequivocal proof of Cannabis smoking.

The authors of this study began with the hypothesis that passive Cannabis inhalation would not exceed the LODs for these assays (i.e., RIA, EMIT and GC-MS) and therefore would not show up creating this very issue.  They designed a study to falsify this hypothesis.  They had five healthy volunteers who had never smoked or used any form of Cannabis before and placed them in an environment with Cannabis smoke for 30 minutes.  All five of those who did not smoke but were merely present for the smoking event immediately after exposure had Delta 9-Tetrahydrocannabinol (THC) concentrations ranging from 1.3 to 6.3

ng/mL.  At the same time total blood cannabinoid levels by RIA were higher than 13 ng/mL in four of the volunteers.  One non-smoker had positive values on the two following days that exceeded the LOD.  In addition to RIA testing, the non-smokers had a blood sample taken, which was analyzed by GC-MS test.  It was preformed according to the typical crime lab’s protocol which called for a LOD cut off of 0.5 ng/mL.  All of the subject non-smokers well exceeded the LOD and tested positive.

In conclusion, as we can see, passive inhalation by being merely present for a Cannabis smoking event can unjustly cause a probationer/parole or motorist in a legally difficult spot.  A positive on RIA, EMIT and/OR GC-MS for Cannabis is not in and of itself conclusive as to source.