 | NORML News: Saliva tests not reliable |
 NORML News, Winter 2007. By Chris Fowlie.
Parliament is set to consider
a new Government bill to
create an offence of driving
under the influence of illegal
drugs, which would have the
same penalties as drink driving.
It is now an offence to drive
while “incapacitated” by
drugs.
Police are already using
field impairment tests - such
as walking a straight line or
balancing on one leg - although
driver’s consent is voluntary.
The new bill is understood to
make the field tests compulsory
if police believed a driver is
impaired.
If they say a driver has failed the test, they will take
an evidential blood sample,
the same as for drink drivers
now. Apparently police will not
conduct random tests.
The Government should
be commended for resisting
the pressure from saliva test
manufacturers who are keen to
expand their businesses and pick
up a lucrative contract.
Saliva tests, like urine tests, do
not detect current impairment
because THC and it’s inactive
metabolite THC-COOH stay in
the body for several weeks after
use (or second-hand exposure).
Not only that, many saliva
tests show false positives. In a
recent review of ten separate
drug testing devices, six recorded
either false negative or false
positive test results for THC.
Five devices recorded false
positive results for THC-COOH.
Manufacturers’ proposed cutoff
guidelines for THC varied widely
from product to product, from
15ng/ml to 600ng/ml. There are
currently no official regulations
governing oral fluid testing cutoff
standards.
Investigators concluded
“reliable detection of marijuana
use in forensic investigations,
such as driving under the
influence and the workplace,
remains problematic.”
Previous evaluations of onsite
oral fluid tests have also shown
the technology to be unreliable
for detecting the presence of
cannabis, particularly when
administered at roadside
checkpoints.
Source: Journal of Analytical
Toxicology, January/February
2007.
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