The National Highway Safety and Traffic Administration has developed three standardized field sobriety tests, one of them being the One Leg Stand test. Police officers in the state of Massachusetts often use this type of field sobriety test to help them determine whether or not a driver is operating under the influence of drugs and/or alcohol. This type of field sobriety test is a divided attention test meaning that officers check for ability to follow instructions as well as physical performance.
When police officers stop a vehicle and suspect a person is operating under the influence, they may ask the driver to step out and perform the One Leg Stand. However, before beginning the test, it is the job of the officer to ensure that the conditions are right for testing. For example, it must be done in a safe area where a person cannot get hurt if they fall. Also, the surface should be hard, dry and flat. If a driver is over 65, more than 50 pounds overweight or has a type of physical impairment then the officer should not have this person perform the One Leg Stand.
Once the testing site is deemed appropriate, the officer must then verbally and physically explain the test. When it is the driver's turn, the person will be required to raise one foot approximately six inches off the ground. While keeping arms at their sides, the driver must count out loud to 30 before placing their foot back down.
During the test, the officer will be observing the driver's actions. If the officer notices swaying, which seems excessive then this counts against the driver. Also, if the person uses their arms to better maintain their balance, this is a score against them. Another part of the scoring relies on if the person puts their foot down. However, the officer can only give one point no matter how many times the person may have put down their foot. Lastly, hopping on one foot to try and maintain balance is also considered a point against the driver.
Like other field sobriety tests, the One Leg Stand is often scored subjectively, meaning the officer could have made some mistakes while scoring.