In Iowa, it is illegal to operate a motor vehicle if you are under the influence of alcohol or drugs. To determine if you have been drinking, officers may ask you to submit to a breathalyzer test. If your blood alcohol concentration is above the state’s 0.08% legal limit, you are apt to face an OWI arrest.

Determining if a driver is under the influence of drugs is more complicated. Still, officers have ways to decide if someone is too stoned to drive. Here are some common ways they identify high drivers:

Watch for signs of impairment 

Impaired drivers typically behave differently than sober ones. As such, an officer may look for behavioral signs. If the officer notices any, he or she may ask you to submit to a breathalyzer test. If the test reveals that you have a normal BAC despite behaving strangely, you may face additional scrutiny to determine if you are under the influence of drugs.

Perform a physical examination 

Strange behavior may be due to physical impairments or medication. Therefore, an officer may ask about your medical history. He or she may also physically examine you to determine if you have dilated pupils or an abnormal heart rate.

Conduct field sobriety testing 

If you are under the influence of drugs, you may not be able to perform certain physical tasks. Accordingly, an officer may ask you to go through a field sobriety test. This may require you standing on one leg, touching your nose, reciting the alphabet or completing other requirements.

Submit a sample for chemical testing 

If you fail a physical examination or field-sobriety test, officers may arrest you on suspicion of operating a vehicle while impaired by drugs. Then, they may ask you to submit a blood or urine sample for chemical testing according to the state’s implied consent law.

Whether you have consumed alcohol or drugs, driving while impaired is a bad idea. Because officers have a variety of ways to determine if you are under the influence of a controlled substance, you put yourself in legal jeopardy if you drive after doing drugs.