No-one has yet explained the technology that will be used with wipes. It's most likely to be Ion Mobility Scanning/ Mass Spectrometry, which is quick to perform, and can detect substances down to the nanogram level.
Cocaine detection in a university population by hair analysis and skin swab testing. Forensic Science International , Volume 84 , Issue 3 , Pages 75 - 86; D. Kidwell
Abstract
The ability to detect cocaine use/exposure by either hair or sweat analysis was compared in a random population of adults at a major US university. Sweat was obtained by wiping the forehead with a cosmetic puff containing isopropanol. Using cut-off levels for sweat of 2.2 ng cocaine/wipe and of hair of 0.05 ng cocaine/mg hair, sweat detected two times more cocaine use/exposure than did hair. Sweat analysis detected a use rate of 12% compared to a 6% rate by hair analysis, both greater than the 2% that would be expected in this population. The high rate of detection was surprising and suggests that use of, if not exposure to, cocaine is underreported. Controlled experiments showed that cocaine could remain on the skin for about 3 days after external exposure. At the current state of knowledge, sweat appears to measure both use and exposure. Nevertheless, sweat testing could be used in several scenarios (such as roadside driving while intoxicated) where the ease of collection and testing of sweat could outweigh the passive exposure considerations. Cocaine concentrations in skin swabs > 15ng/swab would appear to indicate recent use/exposure.
Bold added for emphasis; p_d
I'd expect there to be similar cutoff levels and perhaps even longer periods of detection with amphetamines, which generally have longer metabolic half lives than cocaine.
Edit: I also found this from
NIST, which appears to be from 2006.
A series of practical experiments measured fingerprint IMS spectra as well as the linear dynamic range and detection limits of a series of illicit narcotics including cocaine, heroin, THC and methamphetamine. Typical detection limits for these compounds are in the range of 0.1-100 ng, which corresponds to the detection of a single particle with a diameter of a few micrometers.
Future Plans: NIST researchers will continue a series of experiments using additional IMS instruments in order to establish a recommended alarm threshold level for drugs, further optimize parameters for the detection of a particular drug of interest as well as characterize a list of potential sources of false positives.
If IMS is to be used, then the implications are huge. These devices can detect residues, perhaps even if the surface has been cleaned with alcohol etc. What needs to be remembered is that steering wheels are made of materials designed to absorb sweat, so as to enable a better grip. The first question therefore should be:
Have "Recommedned Alarm Threshholds" been established in relation to the drugs tested for?
afaik, for the less expensive IMS/MS devices, only drugs for which the device is programmed for are detected i.e. only substances with the same charge/mass fragments. While more expensive devices are available that can associate particular mass fragments, say, as with amphetamine analogues, these machines are costly.
Maybe I've underestimated the level of resources available for this, but even so, I'd guess that initially at least, unusual classes of drugs or those not tested for with the oral swabs won't be tested for (there's probably also legality issues associated with adding other drug to the list). The more educated user then would quite likely turn to drugs with a very high potency, for which residues could fall outside the cutoff point, or use drugs which are novel or dissimilar in chemical structure to those tested for.
IMS/MS of course won't be able to distinguish between an amphetamine user with a script, and one using illegally. In the same way that dexamphetamine and selegiline users will test positive with oral tests, IMS/MS will also show a positive.
If (or when) these devices are universally employed, the advantages for LE will be considerable. Cars owned or driven by drug users, whether they're intoxicated at the time or not, would likely be identified as such by the test. Records would be entered into databases and associated with registration numbers, as is other legal stuff that's currently 'tagged' to the owner of a vehicle. So, if you borrowed your mum's car, had a spliff at a party, drove home hours after you were straight and got swabbed, chances are, even if you passed the oral test, your mum would find out sooner or later, either by being notified, or through being swabbed and tested herself, perhaps due to a rego check. With the expansion of intelligent camera systems, rego checks are set to increase big time in the near future.
There's lot's to think about here. I would imagine that once the steering wheel test has been in operation for a while, changes will be made to allow hand swabbing of drivers (defeating the use of gloves). Afterall, it's less invasive than a saliva test. I once predicted that unless reform occurs, we'd eventually see IMS devices installed in every shop doorway. That day now seems a lot closer...
"excuse me Sir, but due to your positive reading when you entered the shop, you'll have to leave. I'm neither legally allowed to serve you, nor covered by my insurance if I do...."
![[eK]](/community/data/avatars/m/90/90959.jpg?1554214546){kind=avatar}
(and the steering wheel too apparently!)