THC COOH (pronounced carboxy THC) is a metabolite of THC delta 9, the psychoactive cannabinoid in pot. THC delta 9 is commonly referred to as just THC, and the carboxy commonly referred to as THC COOH. The COOH metabolite (made by the body FROM the active THC) takes a few hours to become present and detectable, and is thus arguably exculpatory. It is not psychoactive. It is the chemical that for years, and in employment and other contexts has been the subject of the urine tests, and can be found for days, weeks, or even 105 days (longest I've read of). Being lipid (fat) soluble it is the THC COOH that is stored in the fat cells and hangs around for a long time. Since urine sampling and testing is cheap and simple, an employer can use it to fire someone, even though the smoking may have been only on Friday nights with no employment until Monday, and never within any possible impairing time of work.

Impairment generally is gone after 3-5 hours in most people. Some regular smokers (vaporizing being a better alternative) show levels of ACTIVE THC and no impairment days after not smoking. While some experiments have shown 0.5 ng/ml active whole blood after a day or two, and up to 1.5 ng/ml active THC in blood after 5 days, and some claim much higher numbers after even more time, I believe no respected researcher claims impairment after 6-8 hours. Also remember that degree of impairment, while it increases with greater intake, does NOT correlate to level of impairment. A person with 5 ng/ml active THC whole blood (which is what our current (Colorado) law looks at, with NO mention of COOH) might not be impaired at all, while another might be impaired at 3 ng/ml. It seems to vary with many things including the experience of the smoker. In other words, if a person smokes one joint, and is impaired, they will be more impaired after two joints. But the blood-THC measure does not tell us whether or not they are impaired, or how impaired they might or might not be.

For alcohol, drink twice as much and you are more impaired. AND we can say some things about impairment based upon the blood level generally, with the information having meaning for people in general; not just for a specific individual.

With pot, I think there are several factors. First, the max impairment occurs after (30 minutes to 1 1/2 hours) smoking/vaping. Active THC in blood peaks VERY VERY fast, reaching peak levels within minutes of smoking a joint. It also DROPS very very fast in blood. Thus, the blood peaks long before the impairment peaks. This is referred to as counterclockwise hysteresis. Second, as I said, the same number (active THC in blood) does not correlate to the same impairment in two different people.

There are some (not generally accepted stuff) who will testify that the ratio of COOH to psychoative THC delta 9, tells something about recency of smoking. That is utter crap. WAY too many unknowns are missing, and would be necessary to draw such a conclusion.

In court, I have filed and will continue to file, when appropriate, a motion in limine to keep the COOH result excluded entirely since it has zero probative value. It is the same as a prosecutor saying "this defendant had wine within the last weeks or months, we don't know when, we don't know how much, and you should consider that in determining whether they were impaired by wine on the date/time of the charged offense." That would never be permitted and this is no different.

If your active THC # is low enough, that supports the argument that it might have been higher earlier, and the COOH indicates that it had to be hours earlier for the COOH to be made from the THC delta 9 THC, so the smoking had to be at least hours earlier, OR maybe days or weeks earlier, but you can't get COOH until at least hours after the active THC is introduced into the body.

In addition, a side issue I'm dealing with.

When we have a second sample of our clients's blood picked up from a state lab for testing by our private lab, that testing and the request for the sample should never be available to a jury. If the request is in writing, as it normally would be, without protective steps, the "litigation packet" from the state lab may well include the defense request for the second sample. That cannot be permitted, since the second test may be higher than the state's test, or may "confirm" the State's test. There are a number of strategies to avoid this problem.