Unless it is physically impossible to do so, where will a DRE always measure a subject's pulse rate?

The correct answer identifies where a Drug Recognition Expert (DRE) would typically measure a subject's pulse rate when it is not physically impossible. Measuring the pulse at the left radial artery is a standard practice, as the radial pulse is easily accessible and provides a reliable indication of heart rate. It allows for simple palpation and measurement of the pulse in a conscious and cooperative subject.

The left radial position is preferred because it is generally more comfortable for the subject and allows the DRE to maintain a good view of other physiological signs and the subject's overall condition. Accessing the radial artery commonly provides consistent results, which is critical for accurate assessment during a DRE evaluation, especially when determining the influence of drugs on the individual.

Other options may not be practical or standard in this context. Although other pulse sites like the carotid can provide accurate readings, they may be more difficult to access depending on the situation, particularly for an assessment focused on drug impairment. The emphasis on the left radial location aligns with best practices for assessments conducted by trained experts in a variety of environments.