Car crashes involving prescription drugs are often harder to detect and prosecute than those involving alcohol or illicit drugs, the New York Times reported recently. Drunk-driving crashes are declining, but law-enforcement officials say that more people are being charged with driving under the influence of prescription drugs. However, unlike with alcohol, there's no standard for intoxication for prescription painkillers, anti-anxiety medications, and other legal drugs that may or may not be used according to their prescription. Also, taking such drugs (alone or in combination with other substances or alcohol) has widely different effects on different people — all of which makes prosecuting such offenses more difficult.