How can an officer verify a subject's understanding of instructions?

An officer can effectively verify a subject's understanding of instructions by asking them to repeat the instructions back. This method allows the officer to assess whether the subject comprehends what was said and can articulate it clearly. By requiring the subject to restate the instructions, the officer can identify any miscommunications or misunderstandings immediately. When individuals can accurately repeat back instructions, it suggests they grasp the information and are capable of following it as intended, which is crucial in SFST scenarios where clarity of instructions can significantly impact safety and the testing process.

Observing body language, checking for signs of confusion, and timing response speed may provide additional insights into the subject's state of mind or general responsiveness, but these methods do not guarantee a clear confirmation of understanding in the same direct manner that requiring repetition does.