Police officers and sheriff’s deputies often assume that they’e good at detecting intoxication. They report that people smelled of alcohol, acted drunk, or sounded intoxicated because of their slurred speech. And such testimony usually persuades juries.
The officers had taken instruction to recognize intoxication. Researchers also studied experienced bartenders as well as lay people. The results are disappointing. None of these groups are able to identify intoxication with accuracy little better than luck. Yet testimony from police officers or others is sometimes sufficient to obtain convictions. And to send innocent people to jail.
As a result, police often use field sobriety tests. They also use alcohol breath machines. But there are problems with both these techniques.
The problem is serious..
First. Field sobriety tests are highly subjective. They have poor reliability even when properly conducted by trained officers. In fact, 30% of volunteers (with 0.00 BAC) fail them under ideal indoor conditions.
But being pulled over under suspicion of impaired driving is not under ideal conditions. It’s usually dark. Lights are flashing.The surface is uneven. Traffic is rushing nearby. People fear being arrested. It’s hard to concentrate. Yet mistakes count against them. See Never Take a Field Sobriety Test, Say Lawyers.
Second. Alcohol breath testers (“breathalyzers”) don’t actually measure blood alcohol concentration (BAC). The devices only estimate it. Because of their inaccuracy, they may not be able to establish the innocence of those who are not legally intoxicated.
Yet not even a legal BAC reading on an alcohol breath testing machine can always protect a person from arrest. In many jurisdictions, police testimony can override a BAC printout. Even ones that are under the legal limit. Then the court can convict the suspect for DWI or other serious charges.
The only way to prove innocence under some circumstances may be to demand a blood test to determine actual BAC.
Of course, the safest course of action after drinking alcohol is clear. Use a designated driver (DD), take public transportation, or keep BAC well below the illegal level. Even if innocent, it’s best to avoid arrest and trial.
- CO Dept Trans. Colorado Standards for the Standardized Field Sobriety Testing (SFST) Program.
- Goodman, K. and Simon, K. Safe Road Home. Stop Your Teen from Drinking & Driving.
- NH Police Standards and Training Council. DWI Detection and Standardized Field Sobriety Testing.
- TX Parks and Wildlife Dept. Field Sobriety Notes.
- You now know how hard it is detecting intoxication. That’s great incentive to keep BAC very low…or even zero.