Study of rearrests for drunken driving in Norway

Forensic Science International 92 (1998) 21–28

Study of rearrests for drunken driving in Norway S. Skurtveit*, A.S. Christophersen, K.M. Beylich, A. Bjørneboe, J. Mørland National Institute of Forensic Toxicology, P.O. Box 495 Sentrum, 0105 Oslo, Norway Received 9 June 1997; accepted 9 December 1997

Abstract The National Institute of Forensic Toxicology (NIFT) in Oslo receives blood samples from all Norwegian drivers suspected of driving under the influence of alcohol. It is well known that a large proportion of the arrested drunken drivers are repeat offenders. The purposes of this investigation was to find the arrest rates (the percentage of subjects arrested once or more) among drunken drivers followed retrospectively and prospectively during the 11-year period 1984–1994 and the probability of ‘abstaining’ from becoming a recidivist during the 9 years subsequent to the year of selection. By examining the rearrest rates during the 3 following years for drivers selected in 1986, 1989, 1991 and 1992 we tried to look for major effects due to the change in the Norwegian road traffic act of 1988. Altogether 45% of the selected drunken drivers were arrested two or more times. Totally the ‘9-year survival rate’ (i.e. not being rearrested) was 60% for drivers with blood alcohol concentration (BAC) selected from the interval 0.06–0.09%; 56% from BAC 0.13–0.16% and 51% from 0.26–0.29%. The data were further evaluated with respect to frequency of rearrest during 3 years after selection, and was around 30% in 1986, while it was lower for drivers selected in 1992 (19%). An explanation for the reduction in rearrest rate may be the changes in the road traffic act which took place in 1988.  1998 Elsevier Science Ireland Ltd. Keywords: Drunken driving; Rearrest rate; Recidivism; Blood alcohol concentration

1. Introduction The Norwegian road traffic act prohibits driving under the influence of alcohol. The legal limit for driving under the influence of alcohol is 0.05% (0.50 mg / g). Until 1988, *Corresponding author. Tel.: 147 22 042757; fax: 147 22 383233. 0379-0738 / 98 / $19.00  1998 Elsevier Science Ireland Ltd. All rights reserved. PII S0379-0738( 97 )00199-0

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all arrested drunken drivers were sentenced to at least 3 weeks unconditional imprisonment. A change in the Norwegian road traffic legislation law regulating driving under the influence of alcohol and other drugs took place in 1988. This change led to the use of fines and reduced use of prison sentences for driving under the influence depending on the blood alcohol concentration. In addition the drivers license was routinely suspended for 2 years as a consequence of drunken driving both before and after 1988. Blood samples from all Norwegian drivers apprehended for driving under the influence of alcohol or other drugs were analyzed at the National Institute of Forensic Toxicology, Oslo until 1996. The number of drivers suspected for drunken driving has decreased about 50% during the last 10 years [1,2]. It has been documented that a large proportion of arrested drunken drivers are rearrested later for the same offence. A previous Norwegian study [3] showed that more than 40% of the arrested drunken drivers were rearrested during the 5 subsequent years and the rearrest rate was greater for those with high BACs at the time of selection [4]. Studies from several other countries have shown similar results, i.e. high rate of recidivism among drunken drivers [5,6]. The purpose of this investigation was to find the arrest rates (the percentage of subjects arrested once or more) among drunken drivers followed retrospectively and prospectively during the 11-year period 1984–1994 and the probability of ‘abstaining’ from becoming a recidivist during the 9 years subsequent to the year of selection. By examining the rearrest rates during the 3 following years for drivers selected in 1986, 1989, 1991 and 1992 we tried to look for major effects due to the change in the Norwegian road traffic act of 1988.

2. Subjects and methods The study cases were recruited from each of the 4 years 1986, 1989, 1991 and 1992. In total the NIFT received 11 779 blood samples from drivers suspected of driving under the influence of alcohol in 1986, 8842 samples in 1989, 7818 samples in 1991 and 6637 samples in 1992. For each year, 200 drivers samples were selected from each of the following three BAC intervals: 0.06–0.09%; 0.13–0.16% and 0.26–0.29%. The cases were selected randomly from the whole sample material obtained during the respective year. Rather narrow BAC intervals were used to reduce the probability of selecting any driver more than once. Thus, 2400 drunken drivers were included in the study (Table 1). The selected material consisted of 2258 (94%) male and 142 (6%) female drivers. Among the female drivers, 47 had BAC between 0.06–0.09%, 42 0.13–0.16% and 53 0.26–0.29%. A rearrest case was identified as a sample taken on suspicion from the police and received by the institute, regardless of blood alcohol concentration or other drug concentrations in that sample. However, since almost 95% of the samples from drivers suspected for drunken driving received by the institute show a BAC above 0.006% or the presence of other drugs than alcohol, the probability for inducing a ‘false positive case’ as recidivist was low. The number of arrests during the years before and after the year of selection for each

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of the drunken drivers was registered for the period 1984–1994. The cases from 1986 were further investigated prospectively for 9 years up to 1995. The statistical interpretation of the data was evaluated using the chi-squared test, taking P50.05 as the level of significance.

3. Results

3.1. Multiple arrests for drunken and drugged driving A total of 45% (n51080) of the selected drunken drivers were arrested two or more times for driving under the influence of alcohol and / or other drugs during the 11-year period 1984–1994. These 1080 drivers were apprehended 3629 times in total, 893 apprehensions (25%) were due to drugged driving. Table 1 shows the percentage of arrested drivers in relation to the BAC intervals at the time of selection, when the cases were divided between female and male drunken drivers. Samples from female drivers represented 6% of the total selected materials. The percentage of female drivers arrested more than once (32%) was significantly lower than for male drivers (55%) (P,0.001). For both groups multiple arrests were more frequent with increasing BAC. For the highest BAC interval, the percentages of female and male drivers arrested more than once were comparable, 55% and 58%, respectively. In this study, 64 drivers had more than 11 repeated arrests. Altogether they were apprehended 950 times. The number of repeated arrests was in the range 11–34 times. All these drivers were men. The mean age of these drivers, using the age when they first were registered, was 29. The range was 17–52.

3.2. A 9 -year prospective study The 600 drunken drivers selected in 1986, 200 from each BAC interval, were followed prospectively for 9 years (Fig. 1). The figure shows the percentage of these not Table 1 The percentage of subjects arrested more than once among drunken drivers in relation to sex and blood alcohol concentration at the time of selection

Female (%) Male (%) 1 rearrest 2 rearrests 3 rearrests 4–10 rearrests More than 10 rearrests Total

Total

Number of drivers arrested two or more times

BAC 0.06–0.09%

BAC 0.13–0.16%

BAC 0.26–0.29%

142 (6%) 2258 (94%)

45 (32%) 1035 (55%) 491 206 123 196 64

6 (13%) 261 (35%) 129 46 27 49 16

10 (24%) 343 (45%) 168 68 45 52 19

29 (55%) 432 (58%) 194 92 51 95 29

2400

1080

267

353

461

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Fig. 1. Nine-years survival curve of recidivism for various BAC levels at the time of offense used for selection to study.

becoming a recidivist for each year during the period 1986–1995. The curves were plotted similarly to survival curves used in mortality studies, i.e. once a driver was rearrested, he or she was ‘dead’ or ‘out’. The probability for recidivism was highest during the year of selection (11%) and the first following year (15%). There were no differences in the probability of recidivism between the different BAC levels during the year of selection and the two following years. As shown in Fig. 1, the probability of rearrest was higher for drivers selected from the highest BAC interval the first 3 years after selection compared to those from the lowest BAC intervals. Totally, the 9-year survival rate (i.e. not being rearrested) was 60% for drivers selected from BAC interval 0.06–0.09%; 56% from BAC interval 0.13–0.16% and 51% from 0.26–0.29%. Of the drunken drivers rearrested during the 9-year follow-up period, 42% had been arrested at least once previous to the year of selection for drunken driving. Previous rearrests were significantly lower (9%) (P,0.001) for those who ‘survived’ without rearrests during the 9-year prospective study. There were no marked differences in age between drivers who were rearrested and those not. The median age for drivers who were not registered as recidivists during the 9-year period was 27, range 14–73. For those who were rearrested, the median age was 27, range 14–70.

3.3. Rearrest rates for drivers selected in the period 1986 through 1992 The data were further evaluated with respect to the frequency and mean number of rearrests during a 3-year period after selection. Fig. 2 shows that the percentage of

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Fig. 2. Percentage of drivers rearrested during 3 years after selection at a different BAC at the time of the offense used for selection to the study. The number above each column is the average number of rearrests for repeated drunken drivers in each group.

rearrested drivers in this period was around 30% in 1986, while it was lower (21% and 19%) for drivers selected in 1991 and 1992. The reduction in percentage of rearrested drivers was most pronounced for those selected from the lower BAC intervals; for BACs 0.06–0.09% a reduction from 28% rearrests in the 1986 material to 12.5% in 1992 (P,0.001) was recorded and for BAC 0.13–0.16%, a reduction from 31% in 1986 to 18% in 1992 was observed (P,0.01). Fig. 3 shows the percentage of rearrests during the subsequent 3 years for drivers

Fig. 3. Frequency (%) of rearrests with BAC higher than 0.15% for 1986, 1989, 1991 and 1992 during 3 years after selection.

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Table 2 Age of drunken drivers at the time of selection in 1986 and 1992 Age 1986

BAC 0.06–0.09% BAC 0.13–0.16% BAC 0.26–0.29%

Age 1992

Median

Range

Median

Range

22 22 34

15–70 16–50 20–64

25 21 32

15–52 17–59 18–63

with BAC higher than 0.15% at rearrest, in relation to the BAC levels at the time of the selection. As shown in Fig. 3, the drivers selected from higher BAC levels, had a higher frequency of samples with BAC higher than 0.15% at the rearrest. It was found that 80% of the rearrested drivers selected in 1986 with BAC 0.26–0.29% had BAC higher than 0.15% at the time of rearrest. For 1992 this number was 67% (not shown). Cases from 1986 and 1992 were further investigated with respect to age (Table 2) and total number of rearrests. The median age of the selected groups from these 2 years did not differ at the time of selection. For both years, an increased median age with increasing BAC level at selection was observed. The total number of rearrests for drivers selected in 1986 was higher (446) than the number of rearrests for drivers selected in 1992 (237).

4. Discussion Our results showed that 45% of arrested drunken drivers selected from 1986, 1989, 1991 and 1992 during an observation period of 11 years, 1984–1994, were apprehended more than once for similar offenses. As in previous studies from our group [3,4], we found that the chances of rearrest for drunken driving seemed to be higher for drivers with highest BACs at the time of selection to the study. Convicted drunken drivers have been reported to use alcohol frequently in large quantities and tend to demonstrate alcohol-related problems [7]. It has been found that the number of heavy drinkers is greater among those with high BACs at apprehension, and also that the rate of repeat offenses is probably greater among heavy drinkers [8,9]. However, in some other recent studies no relationship was documented between rearrest frequency and BAC level at the time of arrest and the degree to which he / she demonstrated alcohol-related problems [6,10]. A reason for variable findings on recidivism, may be that the behavior is related to differences in the populations studied. Drunken driving offenders are in some countries [6] usually stopped in random road-side controls, while in other countries like Norway, most of them are arrested due to irregular driving or an accident, only about 15% by random road-side controls. Another factor may be national differences in ‘drinking culture’. In some countries, alcohol is a natural part of social life and larger segments of the population may drive under the influence of

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alcohol. In other countries like Norway, driving under the influence of alcohol is a phenomenon among a small part of the population most of which have alcohol-related problems [7]. Such differences may lead to differences in rearrest studies. Previous studies have shown that women constitute a minority of the drivers suspected for driving under the influence of alcohol (7–8%) and drugs (10–11%) [1]. This was also the case when the annual distance driven by women was taken into consideration. In this study, women represented 6% of the selected drivers (independent of rearrest or not), which is somewhat lower than in our previous studies. The lower proportion of women in this study can be due to the selection of BAC intervals above legal limits [1]. Our results showed that female drivers have lower rearrest rates compared to male drivers. The results are in agreement with other recent studies of Yu et al. [6] who reported that male offenders had a higher probability of recidivism than females. An explanation of this trend may be better output from the information campaign among female drivers or that women judge the chance of being controlled by the police and tested for ethanol to be greater than men do. It may also be that a higher proportion of women than men are in the BAC intervals below legal limits, i.e. those intervals which are more difficult to find. The probability of ‘surviving’ from recidivism for drunken drivers is lowest the first year after an offense, independent of BAC at the time of selection. However, after 2 years the prognosis for ‘surviving’ is better for drivers with lower BAC levels. The 3-year prospective study shows that the frequency of rearrests had declined from 1986 to 1992. The total number of rearrests declined |50% for drivers selected in 1992 compared to those selected in 1986. An explanation for the reduction in rearrest rate may be the changes in the road traffic act with fines and sentences which took place in 1988. Thus it is interesting to note that the decrease in rearrest rate is only significant in the lowest BAC interval i.e. among the subjects who were given fines instead of imprisonment. Another explanation is however that the police exerted lower activity on drunken driving. Thus the total number of samples received from suspected drunken drivers was reduced by |30% from 1986 to 1992. It is worth noting that the reduction in rearrests was only significant in the lower BAC interval, i.e. among those who are expected to be least visible in the traffic situation. We did not observe differences in mean age between rearrested drunken drivers selected in 1986 and 1992 which means that drivers arrested in 1992 are not the same drivers. However, the age of the rearrested drivers increased with increasing BAC at the selection. Some studies from other European countries have reported that the introduction of fines have reduced drunken driver recidivism [11,12] which can support the hypothesis that the introduction of fines in the Norwegian legislation had a similar effect. In conclusion, our study showed that repeat traffic offences are very common among Norwegian drunken drivers. Of those apprehended with high BACs (0.26–0.29%) 50% revert to the same offence at least once during a 9-year period. The introduction of fines instead of jail for drunken drivers with BAC below 0.1% in 1988 might have reduced the rate of recidivism, however the apparent rate of drunken driving has decreased by the same factor during this period making conclusions on this point difficult.

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Acknowledgements Thanks are due to John Ulriksen for computer assistance.

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