Vol. 79, No. 4Ask an expert

Police officer tests woman's eyesight.

Identifying impairment

How police can tell if you're driving high

Drug Recognition Experts use a variety of tests to identify impairment, many of which involve the eyes: testing pupil size and tracking how the eyes move. Credit: Martine Chenier

From prescription painkillers to cocaine and marijuana, Drug Recognition Experts (DREs) are trained to identify and convict impaired drivers. Cpl. David Botham has been a DRE with the RCMP since 2010, and has trained more than 200 police officers to recognize the signs of impairment. He sat down with Amelia Thatcher to talk about how drugs impair people, and what signs to look for.

How can you tell if someone is impaired?

Pretty much everybody is familiar with alcohol and what it does to you — it slows you down and reduces your inhibitions. With drugs, they all have some sort of mental effect, but physically they do different things. The crux of the DRE program is based on seven categories of drugs, and each group has certain characteristics or symptoms. For example, blood pressure, pulse rate and pupil sizes can all change depending on the drug. Alcohol falls under one of these categories (it's a central nervous system depressant) but it's treated separately from drugs.

What signs do you look for?

We follow the standards set out by the International Association of Chiefs of Police and the Drug Recognition Evaluation, which is a standardized and systematic 12-step process. As part of that, we do numerous tests on the eyes — the eyes provide us with the most information. First, you make sure the pupils are the same size, because if one is bigger, it may be a medical emergency. Then we test the eyes' ability to track a stimulus. Alcohol will make your eyes jerk when they're following a stimulus from side-to-side, rather than moving smoothly. Lack of convergence or inability to cross your eyes is also an indicator — certain drugs won't let your eyes cross.

We also do divided attention tests where we give the suspect a set of instructions and see how well they perform. There's a walk-and-turn test, one-leg-stand test, modified Romberg balance test and finger-to-nose test. The totality of those tests shows impairment, if they can't perform them well then they probably shouldn't be driving.

We also check if their vital signs are in the normal ranges — pulse rate and blood pressure. This can be a major clue as to what category of drug they're on. Then we look at the body and do a muscle tone examination. Certain categories of drugs make your muscles do funny things. With narcotic analgesics [painkillers] your muscles will be very flaccid, almost like a bag of milk. With stimulants, you're going to be very rigid and tense. We also look for injection sites.

We'll then interview the suspect to see what they have to say. They're under no obligation to say anything, but a lot of the time we can have very candid conversations about what drugs they've taken.

Finally, if we believe a person is impaired at the end of the evaluation, we ask for a urine, blood or other fluid sample for the lab.

What do you come across the most?

Cannabis is probably the most popular across the country — in Nova Scotia for sure — followed by stimulants [cocaine, methamphetamine] and narcotic analgesics [painkillers]. We come across just about every category of drug, but a lot of it is regionalized. Rural Newfoundland was surprisingly more opiates, while Halifax was more stimulants like cocaine. It depends on the drug trends in the area.

Where are drugs the biggest issue?

It's both urban and rural. Having now worked in my fourth division [province], I've learned that there's drugs and alcohol in every community. Prescription drugs are also huge, there might be no intent, but somebody could be impaired by what a doctor prescribes them, and they can still be charged.

What would you say toother police officers?

Be aware of what isn't normal. There was one instance where I drove past a guy I knew and waved, but he didn't wave back. He always waved at me so I drove back and checked it out. It turned out he was driving drunk. Drugs and alcohol influence behaviour, so if someone is acting out of the ordinary from what you expect, look into it a bit more because you don't know what the cause could be.

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