What a Roadside “Field Impairment Test” Involves


Remember a “Field Impairment Test” is totally different from a roadside swab test and has a different purpose. The purpose of a “field Impairment Test” is to determine whether or not a suspect is impaired, and therefore “unfit” to drive: not whether he/she is driving over a specific drug driving limit. It is important also to bear in mind that a “Field Impairment Test” can only be carried out by a specifically trained police officer: not every police officer is trained to carry out such tests. Also note that though these tests are often described as “Field Impairment Tests”, they are not always completed at the roadside.

i) An examination of your pupils, during which the officer will tell you to look straight ahead, whilst keeping your eyes open. A gauge will then be used, held adjacent to the side of your head, to ascertain the size of your pupils.

ii) The “Modified Romberg Balance Test”. The officer will direct you to stand up straight, with your heels and toes together, and arms down by your side. He/she will tell you to maintain that position. You will then be told to tilt your head back and close your eyes. After this you will be told to bring your head forward, open your eyes and say the word “stop” after you, not the officer, think that 30 seconds has passed. The officer will check your estimation of 30 seconds with his own watch and note how well, generally, you carry out the test.

iii) “The walk and turn test” involves just that and should be demonstrated to you, by the officer, before it’s your turn. He/she should identify a straight line, away from any kerb, and will then ask you to place your left foot on that line. After that you will be instructed to place your right foot in front of the left so that they are heel to toe. You should be told to keep your arms to your side and take 9 heel to toe steps, counting out aloud each step as you take it. You will then be told to turn around and repeat the exercise. All the while your actions will be noted down and any deviation in keeping to the straight line, marked on the documentation being completed by the officer, together with any other items of potential interest; i.e. whether you started to soon, failed to turn correctly, etc., will be similarly noted.

iv) “The one leg stand test” begins with the officer telling you to keep your legs together, with your arms by your side, before you are given further instructions. You will then be told to raise your right leg between 6 and 8 inches (15 to 20 centimetres) off the ground. He/she will expect you to keep your right foot parallel with the ground and look at it whilst you, over 30 or so seconds, count up, not to yourself but aloud, “one thousand and one”, “one thousand and two, “one thousand and three” and so one. The officer may then, though he/she does not have to, ask you to repeat the exercise with your left foot. During the whole procedure the officer will take a note of any point at which you sway, hop or generally lose your balance, together with the point at which, during the test, this occurred.

v) “The finger to nose test” is described as a test of depth perception and balance. You will be told to stand with your feet together and, whilst doing this, bring both arms up in front of you, with the palms uppermost, and your fist closed; apart that is from your index finger of each hand, which you will be told to extend. What this all means should be demonstrated to you by the officer, before you are asked to complete the task. You will then be instructed to hold that position whilst the other instructions are given. You will then have to tip your head back slightly and close your eyes. After this you must touch your nose with the index finger of your right or left arm (the choice of which is for the officer to make), whilst all the while maintaining your posture and keeping your eyes closed. The officer will then will then instruct you to repeat the exercise by calling out, in the following order, “left”, “right”, “left”, “right”, “right”, “left” whilst all the while noting your ability to both follow instructions and carry out those instructions.


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