Physiological Effects on the Human Body in Relation to K-9 Performance

How does drug use in the human body correlate to a K-9’s performance? Here is an example of a K-9’s boundaries and an officer’s inability to recognize and comprehend the K-9’s limitations in drug work.

An officer stops a vehicle for a minor traffic violation and upon contact with the operator immediately notices the subject appears to be nervous, sweating, and his pupils are visibly dilated. (The colored portion of the eye or the iris is hardly visible.)  The officer requests consent to search the vehicle and consent is denied. The officer believes he has sufficient reasonable suspicion to hold the vehicle and employ the use of his K-9 partner to search the exterior of the vehicle. The K-9 searches the exterior and gives no indications. The handler becomes aggravated believing his partner failed in his duties and completes the traffic stop questioning his partner’s reliability. The K-9 did his job, however, the K-9 was not trained to indicate on the household spice nutmeg the individual had in his possession, which he had also been consuming. (That’s correct, NUTMEG.)

The officer comprehended the signs and symptoms of drug use, however, he failed to understand the physiological effects of different categories of drugs on the human body.

Looking at a person’s eyes is one of the first telltale signs of drug use. Certain drugs will cause the pupils to dilate while other drugs cause constriction of the pupils. Still other drugs cause no effect on pupil size; however, they do cause Horizontal Gaze Nystagmus and Vertical Gaze Nystagmus. Officers trained in the Standardized Field Sobriety Tests were originally trained that Vertical Nystagmus inevitably meant drug use. This is not the case, as the only drugs that will cause Vertical Nystagmus are also the only drugs that will cause Horizontal Gaze Nystagmus.

If a person uses Stimulants, Hallucinogens or Cannabis the pupils of the eye will become dilated. If constricted pupils are observed, then the drug used would be a Narcotic Analgesic. A person using Depressants, Inhalants, or PCP will have Horizontal Gaze Nystagmus, however, pupil size will remain normal.

Stimulants such as Cocaine and its bases, Methamphetamine, Amphetamines, Methcathanone, Khat, and a long list of others, will cause pupil dilation along with numerous other physical effects.

Hallucinogens such as Peyote, LSD, Psilocybin Mushrooms, MDMA, PMA, MDA, Nutmeg, and of course many others cause pupil dilation along with numerous other physical effects.

Cannabis, which includes drugs like Marijuana, Hashish, Hashish Oil, Marinol, causes pupil dilation along with numerous other physical effects.

As we look at Narcotic Analgesics drugs like Heroin, Opium, Methadone, Darvon, and Demerol, they cause constriction of the pupils and again other physical effects. 

Each category of drugs will create different physiological effects on the body, however, those effects are predictable within each category. We have to understand the limitations of the K-9’s, and the more we educate ourselves about controlled substances and over-the-counter drugs the better we will be able to utilize K-9’s in a more effective manner.

The United States has only 5% of the world population, yet, consumes 60% of the world’s illegal drugs!  As you can see, K-9’s are not trained to indicate on all of the different types of controlled substances and certainly not the thousands of prescribed or over-the-counter drugs.

     Thank you,
     Joe Keil
     Manitowoc County K-9 Handler
     and Wisconsin Drug Recognition Expert