The use of an alcometer in clinical forensic practice

Journal of Clinical Forensic Medicine (1995) 2, 177-183

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The use of an alcometer in clinical forensic practice D. J. Rogers, M. M. Stark, J. B. Howitt

Forensic Physicians, London, UK SUMMARY. Forensic physicians are at times required to provide a professional opinion on a person's degree of intoxication through alcohol, particularly with regard to fitness for interview by the police. Inherent to these assessments is an estimation of the blood alcohol concentration (BAC). Most forensic physicians rely on taking a history regarding recent alcohol consumption and a clinical assessment to estimate the BAC. We report a study in which the BAC of 118 detainees was estimated and compared with the BAC measured by an alcometer. Our estimations were accurate in 66% of cases. Most errors resulted from underestimating the BAC. Additionally, we attempted to determine fitness for interview using a single measurement of the BAC without a clinical assessment. 19% of those who were assessed as unfit for interview had a BAC of less than the UK legal limit for driving (currently 80 rag%) and 37% considered fit, had a BAC above that level. We conclude that the routine use of alcometers would enhance the practice of forensic medicine but could not replace its role in the assessment of levels of alcohol intoxication. Journal of Clinical Forensic Medicine (1995) 2, i77-183 Table 1. Medico-legalassessments in which degreeof intoxicationis relevant

Since the introduction of the Criminal Justice Act, 1925,1 with which it became an offence for a person to be drunk whilst in charge of any mechanically propelled vehicle, forensic physicians (police surgeons, forensic medical examiners) have been asked to provide a professional opinion on a person's degree of intoxication through alcohol. Over the years the work of a forensic physician has changed. Assessments of intoxication under the R o a d Traffic Acts have considerably decreased since the advent of analytical tests to determine objectively a person's blood, urine or breath alcohol concentration. However, a professional opinion regarding the degree of intoxication due to alcohol remains of considerable importance in a number of other medico-legal assessments (Table 1). For example, alcohol has been found to be a significant factor in 39% of the 964 fitness for detention assessments that were undertaken by one forensic medical examiner ( F M E ) . 2 The Codes of Practice for the Police and Criminal Evidence (PACE) Act, 1984, state that 'No person, who is unfit through drink or drugs to the extent that he is unable to appreciate the significance of questions put to him and his answers, may be questioned about an alleged offence in that condition ...'.3 No legal guidance

• • •

Fitness for detention Fitness for interview Fitness for charging

• , • • • • •

Fitness for release Fitness to drive Drunk on licensedpremises Drunk in charge of a child under 7 years MentalHealth Mensrea In relation to Transport and Works Act 1992

is given in the PACE Act 4 as to who should assess fitness for interview but the Codes o f Practice say that 'The police surgeon can give advice about whether or not a person is fit to be interviewed ...'. During 1994, a medical opinion regarding fitness for interview was requested in 43% of the total cases seen by one author (D JR). Although there are many considerations to be taken into account when assessing fitness for interview, the level of intoxication from alcohol is of major significance. A research study commissioned by The Royal Commission on Criminal Justice s noted that intoxication with alcohol was the main reason a person was considered to be unfit for interview and yet there was no objective measure employed by which to assess it. An opinion has been offered that a detainee is not fit for

D. J. Rogers MBBS, MRCGP, DMJ, M. M. Stark MBBS, DMJ, J. B. Howitt MBBS, D M J , Forensic Physicians, London, U K . Correspondence to: D. L Rogers, 18 Rosehill F a r m Meadow, Banstead, Surrey SM7 3DE, U K . 177

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Journal of Clinical Forensic Medicine

interview if the blood alcohol concentration (BAC) is above the legal limit for driving, which in the UK is currently 80 mg in 100 ml of blood (mg°/o).6 Clarke 6 opined that it would be an advantage to have an alcometer available to police surgeons. It has also been suggested that, when no medical or drug related complications are suspected, police officers could use an alcometer to determine when someone who is drunk might be fit for interview and thus obviate a medical assessment. 7 At present in the UK only a few police surgeons have access to alcometers. In the absence of such a measuring device, a rough estimate of the BAC can be made by taking a history of the quantity and strength of alcoholic beverage that has been consumed over a period of time, followed by a clinical examination for evidence of alcohol intoxication. The purpose of this study was two-fold. Firstly, to determine whether experienced forensic physicians could estimate a person's BAC based on clinical assessment alone and secondly to see if it is possible to determine fitness for interview using an isolated measurement of the BAC. The study was conducted in eight Metropolitan Police stations over a 3 month period (October to December 1994).

risk of contamination. If for some reason the person is unable to provide the sample themselves, a manual sample can be obtained by the operator activating the machine as the person exhales. Tests can be run every 2 minutes. In the case of an unconscious person, a nasal sample can be obtained by closing the mouth and placing the mouthpiece in a nostril. The nasal reading equals 90% of the equivalent oral sampleY The portability of the machine facilitates its use in a cell when necessary, for example with semi-conscious or confused detainees. Research with the precursor of the Alco-Sensor IV, the Alco-Sensor III, in emergency departments and intensive care settings using a passive nasal breath sampling method showed that it provided a means of rapidly estimating the BAC and thereby facilitating diagnosis and treatment. 9 In common with other alcometers that are available, the accuracy of the Alco-Sensor IV must be checked on a regular basis. The machines used in this study were checked each month and they all maintained accurate calibrations.

Patient population MATERIALS AND METHODS

Measuring device Alcometers are automated breath alcohol testing machines that provide an immediate digital readout, are easy to use and ideally suited to our purposes. Three Alco-Sensor IV alcometers were lent to us, by the manufacturers Intoximeters Inc. (Redhill, UK), for the period of the study. The Alco-Sensor IV is a robust, pocket-sized instrument which automatically samples deep lung breath and converts the result into a BAC equivalent, in a three digit readout, up to 400 rag%. The instrument is alcohol specific and will not produce false positive results. Insertion of the mouthpiece turns the unit on and the display panel informs the operator when the machine is ready. Usually the unit is ready for use within seconds but if the unit has cooled to below the operating temperature of 10°C there may be a slight delay as it warms. When capable, the subject is asked to stand up, to keep their arms by their sides and to blow into the mouthpiece. The machine clicks as soon as an adequate sample has been provided. The mouthpiece has low resistance making it easy for the subject to provide a sample. The mouthpieces are disposable and no suckback is possible, both of which ensure that there is no

The patient population consisted of all detainees seen consecutively who were examined for fitness for detention, fitness for interview, fitness for release, fitness for charging and mental health assessments when the police believed that they may have consumed alcohol prior to their arrest. Detainees arrested for road traffic offences and other offences where the BAC could have had direct implications on the charge, for example drunk on licensed premises, were specifically excluded. Consent was obtained from the detainees who were willing to co-operate with the study.

Proforma The proforma included the reason for the examination, basic demographic details, self-reported alcohol consumption in the previous 24 hours and the average weekly consumption of alcohol. The latter was requested in order to gauge each participant's likely rate of alcohol metabolism. The participants were asked not only about the volume and type of alcoholic beverage consumed but the make of the beverage and the strength. This information was then converted into standard units of alcohol (a 'standard' unit is 8-10 g of alcohol) using recognised tables, lo

The use of an alcometer in clinical forensic practice

Assessment A comprehensive clinical assessment was conducted in each case. The parameters which were used to determine fitness for interview are shown in Table 2. Following the clinical assessment each participant was placed in one of the following three categories: 1. BAC < 80 rag%, 2. BAC 80-160 rag% 3. BAC > 160 mg% Our clinical opinion was then conveyed to the detainee and the police. Each individual then provided a sample of breath (either automatically or manually). The alcometer reading was recorded only on the proforma, not in the clinical records. The reading was not revealed to the police or to the detainee, nor did we change our original (clinically determined) decisions.

RESULTS

Age/sex distribution In the 3 month study period, 118 people agreed to take part in the study. 90% (n = 106) of the participants were male. The age of the participants ranged from 17-64 years (two persons did not know or declined to tell us their age). 46% of the participants were aged between 20 and 29 years.

number of assessments conducted (166) and the total number of participants.

Recent alcohol consumption (Fig. 1) 26% (n = 31) of the participants were unaware of, or unwilling to provide, details regarding how much alcohol they had consumed within the preceding 24 hours. The majority of the people who were able to estimate their intake said that they had consumed between 1 and 10 units of alcohol, the equivalent of one-half to five pints of ordinary strength beer. Probably the most accurate answer came from the man who said that he had drunk 18 cans of high strength lager, the equivalent to 72 units; he was unable to provide a sample automatically and the manual testing showed him to have a BAC of 323 rag%. The person who denied having consumed alcohol produced a zero reading on the Alco-Sensor IV, although be admitted to having taken other intoxicating substances.

Weekly alcohol consumption (Fig. 2) 39% (n =46) of the participants were unable, or unwilling, to respond to this question. 2% (n=2) said they did not normally drink alcohol, 28% (n= 33) said that they drank less than 21 units per week, 13% (n= 15) estimated that they consumed 21-42 units per week and

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Reason for assessment The majority of assessments, during which the AlcoSensor IV was used, were for fitness for interview (n = 80, 68%) and fitness for detention (n=71, 60%). The remaining assessments were for fitness for release (n = 9, 7%) fitness for charging (n = 2, 2%) and consideration of mental health (n =4, 3%). In some consultations two or more parameters were considered which accounts for the disparity between the Table 2. Parameters used to determine fitness for interview History: .

, • • • • • •

Basic details (name, date of birth, address, postcode, age) Orientation and awareness o f procedures Past and current medical problems Medication (OTC/Prescription) Drugs and alcohol consumed Education Occupation Recent sleep and meals

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19% (n=22) estimated that they drank more than 42 units per week. Assessment of BAC In our opinion, 41% (n=48) of the participants had a BAC of less than 80 rag%, 36% (n=43) had a BAC between 80 and 160 rag% and 23% (n=27) had a BAC over 160mg%. We compared these results with the alcometer readings which were sub-divided into the same categories. Aleometer reading < 80 rag% (Fig. 3) There were 42 people whose BAC reading was less than 80 rag%, 81% (n = 34) of whom were accurately assessed. We overestimated the BAC in seven people in this group. However, three of these apparent overestimations were actually in the upper range for the category (i.e. 76 rag%, 74 rag% and 75 rag%) and four of the seven (including one person in the upper range of the category) admitted, during the clinical assessment, to having used other potentially intoxicating substances, for example benzodiazepines. There was one person who was clinically assessed to have a very high BAC (greater than 160rag%) but whose alcometer reading was less than 80 rag%. This result is believed to represent a user error as the sample was obtained manually and the machine may not have been activated at the end of expiration, as recommended for such samples. On the few occasions that manual

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samples were necessary (for example because of poor co-ordination) the authors found it difficult to assess when the end of expiration had been reached. Alcometer reading 80-160 rag% (Fig. 4) There were 40 people whose BAC reading was between 80 and 160mg%, only 55% (n=22) of whom were accurately assessed. Again, three of the overestimations were at the upper range of alcometer category (readings 160mg%, 160 rag%, and 152 mg% - nasal). The majority of our errors in this group were the result of underestimating the BAC. There were 14 people with a higher BAC than we had predicted and only three of those 14 were in the lower limit of the category (80 mg%, 82 rag% and 90 rag%). Alcometer reading > 160 mg% (Fig. 5) Finally, there were 36 people whose BAC reading was greater than 160mg%, 61% (n=22) of whom were accurately assessed. As with the above group the majority of our errors were the result of underestimations of the BAC which occurred in 14 cases. Only four of these were in the lower range of the category (166 mg%, 163 mg%, 170 rag% and 170 mg%).

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Fitness for interview A total of 83 assessments for fitness for interview were conducted, 51% (n = 42) of whom were considered unfit.

181

Table 3 shows the categorised alcometer readings for each person related to our conclusions regarding their fitness for interview. Of the people found to be unfit for interview, 19% (n=8) had a BAC below the legal limit for driving (80 mg%) and 37% (n= 15) of people considered fit for interview had a BAC above 80 mg%. Unfortunately, because of the few responses to the question regarding normal weekly alcohol consumption, it was not possible to reach any significant conclusions as to whether the latter group were normally high alcohol consumers.

DISCUSSION The accuracy of the clinical assessment in determining the BAC In the UK the majority of forensic physicians continue to rely on the available history regarding recent alcohol consumption and a clinical examination for evidence of intoxication to estimate a detainee's BAC, despite the fact that both of these parameters are subject to a number of inaccuracies. The unit system used for monitoring alcohol consumption has been found to have serious inaccuracies when applied to high strength drinks 11 and it has long been recognised that the degree of mental and physical impairment for a given BAC varies widely between individuals.12 Attempts to produce a reliable and valid clinical assessment by which to measure alcohol intoxication t3 have been shown to be unreliable, particularly in chronic alcohol abusers with a high tolerance to the visible effects of alcohol. 14 Trained observers could only identify between 50 and 67% of alcoholic subjects who were intoxicated but gave invalid self reports. 15 One way of conducting this study would have been to use salivary alcohol measuring devices. The value of these devices in the assessment of individuals under (or apparently under) the influence of alcohol in the custodial setting has already been described) 6 Saliva alcohol measuring devices provide an immediately available accurate result but personal experience in our forensic practices revealed that it is often difficult to obtain sufficient saliva for a reading. The alcometer avoids these problems. Table 3. Conclusion regarding fitness for interview based on clinical assessment Actual BAC

Fit for interview

Not fit for interview

< 80 m g % 80-160mg% > 160mg%

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182 Journal of Clinical Forensic Medicine Clinically, we correctly assigned 66% o f cases to the appropriate B A C category (as defined by the alcometer reading). This degree o f accuracy is p r o b a b l y acceptable for m a n y o f the assessments undertaken b y forensic physicians, in so far as it is usually the degree o f intoxication, rather than the actual BAC, that is relevant in the clinical setting. However, there are occasions when accurate information on the B A C is vital to the clinical assessment, for example in differentiating between drug and alcohol intoxication, and in such cases an alcometer w o u l d be invaluable. There are a n u m b e r o f alcometers available. The Alco-Sensor IV was easy to use and provided a rapid and reliable BAC, thereby potentially facilitating diagnosis and treatment. The portability and m a n u a l m o d e o f the machine makes it extremely useful in a police cell where a nasal sample can be taken in an unconscious patient.

Table 4. Some crimes which require specificintent to be formed • • • • • •

Murder Grievous bodily harm with intent Theft Robbery Burglery with intent to steal Handling stolen goods

Medico-legal implications W h e t h e r the B A C reading obtained in these circumstances would be admissible in evidence remains to be seen. In certain crimes ( T a b l e 4 ) which require the f o r m a t i o n o f specific intent, self induced intoxication m a y negate the mens rea and therefore be considered as a defence. ~7 The evidence o f the forensic physician with respect to the examination o f the detainee and the record o f the alcometer reading in the medical notes m a y be used as evidence in court proceedings. Some alcometers (e.g. Alco-Sensor I V ) allow for a dated print-out to be produced.

Fitness for interview Standardised criteria to determine fitness for interview have yet to be defined. M a n y doctors currently rely on the detainee's correct orientation in time and place, his capacity to understand questions and to p r o d u c e relevant and rational answers. 5 We consider that to be fit for interview a person m u s t have an understanding o f the proceedings. Therefore, during our assessments, for fitness for interview, a comprehensive functional assessm e n t is carried out involving n o t only a physical examination but also determination o f the mental state. This study f o u n d that an isolated measurement o f the B A C was n o t a reliable predictor o f fitness for interview and as such demonstrates that the use o f an alcometer c a n n o t replace a medical assessment. D u r i n g the clinical assessment, eight people were f o u n d to be unfit for interview despite a B A C o f less than the legal limit for driving. These people were considered unfit for a variety o f reasons including being affected by other intoxicants which the alcometer specifically excludes. Conversely, 15 people w h o h a d B A C s over the legal limit were considered fit for interview. It could be postulated that the latter g r o u p consisted o f people who regularly c o n s u m e d large a m o u n t s o f alcohol and w h o were therefore less likely to show evidence o f intoxication. Unfortunately, due to limited information on n o r m a l drinking patterns, we were unable to reach this conclusion. To declare these 15 as unfit for interview on a B A C alone would have potentially increased the time they spent in c u s t o d y with personal and resource implications.

Acknowledgements This research has been supported by a grant from the W. G. Johnston Memorial Trust, Association of Police Surgeons. The Alco-Sensor IV alcometers were lent to us by Metron Instruments Ltd (Darby House, Bletchingly Road, Merstham, Redhill, Surrey RH13DN), with the consent of the manufacturers Intoximeters Inc. The research was carried out with the permission of the Metropolitan Police, London, UK.

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