Assessment in the Field by Police

In the United Kingdom, if a police officer stops a driver, for whatever reason, and believes the driver is unfit to drive, it is highly likely that a roadside breath test will be conducted. That is not the case in the United States, where field breath testing is only permitted in some states, and then only for drivers under the age of 21 years (22). The laws of the United States also prevent random breath testing. Under the Fourth Amendment, searches and seizures must be reasonable. Stopping a vehicle is a seizure, but it may be reasonable if the police officer has a justifiable suspicion that an offense is being committed. The procedures American officers follow in driving under the influence cases are surprisingly similar to the procedures under the United Kingdom Section 4 RTA. To gain powers to conduct further tests, officers in most US states first have to be satisfied that the driver is impaired. This then gives them the probable cause to carry out subsequent tests similar to the Section 4 procedure to prove impairment.

If breath testing is negative, impairment resulting from drugs or medical illness must be considered. Until recently in the United Kingdom, police traffic officers received little or no training in the recognition of signs and symptoms of drug effects. However, a pilot study (86) was carried out in England, Wales, and Scotland in 1999, whereby police officers were trained to perform roadside impairment tests; this study showed that forensic analysis confirmed the presence of a drug in 92% of the drivers who were suspected of taking a drug, who had failed the field impairment tests (FIT) and who had provided a sample. As a consequence, FIT is now slowly being introduced across the United Kingdom. This contrasts dramatically with the United States, where in 1979, the Drug Recognition Expert (DRE) Program was introduced. Police officers were trained to observe and document known indicators of drug use and impairment.

Instead of breath testing, a series of standardized field sobriety tests, which include psychomotor and divided attention tests, is conducted. If alcohol is suspected, the following tests are carried out: walk and turn test, one-leg stand, and the horizontal gaze nystagmus test. In addition, if drugs are suspected, a Romberg balance test is also carried out. Unlike chemical tests (with refusal to submit possibly resulting in immediate license suspension), drivers in the United States are not legally required to take any field sobriety tests; however, if the driver submits, the results can be introduced as additional evidence of impairment.

These tests are all divided attention tests, which assess the individual's balance and coordination, as well as the ability to follow simple instructions (i.e., to divide attention between multiple tasks). They are as follows:

• Horizontal gaze nystagmus: nystagmus may be caused by any number of conditions, but its presence could indicate drugs or alcohol.

• Walk and turn: nine steps heel to toe are taken in one direction, and then the individual turns and repeats the process in the other direction. Eight impairment indicators are measured; if two of the eight are present, impairment would be indicated.

• One-leg stand: the subject has to stand on alternate feet for 30 s while counting aloud. Failing two of the four recognized indicators would indicate impairment.

• Romberg balance test: the subject stands with eyes closed and estimates a period of 30 s during which body sway is estimated. Some drugs alter the body's internal clock and make the person act faster or slower than normal. The test allows for a tolerance of ±10 s.

If impairment is identified and alcohol is suspected, the driver performs a breathalyzer test and a similar procedure to the United Kingdom Section 5 RTA procedure is conducted. However, if drugs are suspected, the police officer would call on a DRE to carry out a more detailed examination.

The DRE will use a 12-step procedure as follows:

1. Breath alcohol test: this is carried out by the arresting officer; if the reading is not consistent with the degree of impairment, the DRE is called in.

2. Interview with the arresting officer: the purpose is to ascertain baseline information, including the circumstances of the arrest, whether an accident occurred, whether drugs were found, and if so, what they looked like.

3. Preliminary examination: the purpose of the preliminary examination is to determine whether if there is sufficient reason to suspect a drug offense and to try to exclude any underlying medical problems. General observations and details of any current medical problems are ascertained, and the first measurement of the pulse is taken. If no signs of drug influence are found, the procedure is terminated; if any medical problems are found, a medical assessment is obtained, and if drugs are still suspected, a full assessment is carried out. If at any time during the assessment a serious medical condition is suspected, a medical opinion will be obtained.

4. Eye examination: the driver is assessed for horizontal gaze nystagmus, vertical gaze nystagmus, and convergence.

5. Divided attention tests: once at a police station, the Romberg balance test, walk and turn test, one-leg stand test, and the finger-to-nose test are carried out. These are all examples of divided attention tests whereby balance and movement tests are performed in addition to remembering instructions.

6. Vital signs examination: blood pressure, temperature, and a second recording of the pulse are carried out.

7. Darkroom examination: pupil size is measured in room light and then in near total darkness, using both indirect artificial light and direct light. The mouth and nose are also examined for evidence of drug use.

8. Muscle tone: limb tone is assessed as some drugs cause rigidity, whereas others, for example, alcohol, cause flaccidity.

9. Injection sites examination: the purpose is to seek evidence of intravenous or injection drug abuse. A third pulse reading is taken.

10. Interrogation: a structured interview about the use of drugs is carried out.

11. Opinion: based on all the previous assessments, the DRE forms an opinion as to drug impairment and also the type of drug causing the problem, the legal standard being a reasonable degree of certainty.

12. Toxicology testing: at the same time, samples are obtained for toxicological examination, either a blood or urine sample being taken for analysis of common drugs.

Initial studies, suggesting high sensitivity and specificity for DRE examination (87), have not been confirmed in controlled laboratory studies. The results of the few studies that have been performed suggest that the accuracy of DRE assessment in general may not be sufficiently good to provide evidence in court fairly (70,71). Several field studies have indicated that a DRE's opinions were confirmed by toxicological analysis in 74-92% of cases when DREs concluded that suspects were impaired. However, published controlled trials, in which blood levels were measured before and during DRE examination, have shown that except in the case of alcohol, DRE assessment agreed with toxicology findings only 32-44% of the time.

There are other options for roadside screening tests. Both sweat and saliva have been used (88). Devices are already available, and some have been approved by the US Department of Transportation for the testing of commercial drivers. The mere detection of a drug does not prove impairment unless, of course, the jurisdiction has per se laws whereby the detection of drugs at some predetermined level is ruled, by law, to be proof of impairment. Roadside drug screening tests are acceptable to the public; a UK study (89) found that 98% of drivers were in favor of the principle of road side drug screening and found the test methods of saliva or forehead perspiration generally acceptable. The UK Home Office Police Scientific Development Branch are currently researching the use of computer program for detecting impairment and Surface Enhanced Raman Spectroscopy as a means of quantitative analysis of saliva for drugs.

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