Banner-Evaluation of Minnesota's High-BAC Law

3. Evaluation of Minnesota's High-BAC Law

Profile and Disposition of DWI Cases 1997-2000

Alcohol Test Results

In both years 1998 and 2000, the distribution of alcohol test results between first-time and repeat offenders was statistically different (1998: X2 = 1,021.4, df = 5, p < .001; 2000: X2 = 1,230.4, df = 5, p < .001) (Table 2). Also in 1998 and 2000, a test refusal was almost twice as likely among repeat offenses as among first-time offenses (22.7 percent vs. 11.5 percent in 1998 and 22.4 percent vs. 10.5 percent in 2000).

Table 2

Alcohol Test Results for First-time and Repeat DWI Offenses
Minnesota, 1998 and 2000

 

1998

2000

Type of Offense

1st

Repeat

Total

1st

Repeat

Total

 

%

%

%

%

%

%

.01-.14 BAC

35.8

23.6

32.3

38.6

26.3

35.1

.15-.16 BAC

14.8

11.7

13.9

14.7

11.7

13.8

.17-.19 BAC

16.9

16.2

16.7

17.4

15.5

16.9

.20+ BAC

16.9

21.0

18.1

15.5

20.4

16.9

Refusal

11.5

22.7

14.7

10.5

22.4

14.0

Unknown

  4.2

  4.7

  4.3

  3.2

  3.7

  3.3

TOTAL

(N)

100%

(23,996)

100%

(9,666)

100%

(33,662)

100%

(25,520)

100%

(10,217)

100%

(35,737)

 

X2 = 1,021.4, df = 5, p < .001

X2 = 1,230.4, df = 5, p < .001

In 1998, 16.9 percent of first-time offenses and 21.0 percent of repeat offenses involved a BAC at or above .20 (Table 2). The percentages of high-BAC offenses remained at these levels in 1999 and declined slightly in 2000 to 15.5 percent of first-time offenses and 20.4 percent of repeat offenses. The differences between the 1998 and 2000 patterns of alcohol test results for all BAC categories, including test refusals and unknown BAC test results, were statistically significant for first-time offenses (X2 = 84.5, df = 5, p < .001), and for repeat offenses (X2 = 28.8, df = 5, p < .001).

The test refusal rate for first-time offenses gradually declined from 12.7 percent in 1997 to 11.5 percent in 1998, 10.7 percent in 1999, and 10.5 percent in 2000. This decline was statistically significant (X2 = 106.3, df = 3, p < .001). For repeat offenses, the test refusal rate was essentially unchanged from 22.2 percent in 1997 to 22.7 percent in 1998, 22.0 percent in 1999 and 22.4 percent in 2000 (X2 = 1.11, df = 3, p = .774).

Profiles of 1998 alcohol test results by gender and age category for first-time and repeat offenses appear in Table 3. (The distribution of these demographic characteristics across alcohol test results was similar for 1999 and 2000.) First-time offenses committed by women were slightly more likely than offenses committed by males to involve a high BAC and slightly less likely to involve an alcohol test refusal. Female repeat offenders were more likely than males to have a high-BAC test result. (However, as males committed the large majority of first-time and repeat offenses, they also represented the majority of offenses involving high BACs and alcohol test refusals.) With the exception of first offenders age 55 and older, increasing age was associated with an increasing proportion of high-BAC test results among first and repeat offenders. Test refusal rate was the highest among 35-54 year-old first and repeat offenders.

Table 3

Alcohol Test Results for First-time and Repeat DWI Offenses by Gender and Age Category
Minnesota, 1998

   

<.20 BAC

>.20 BAC

Refuse

Missing

First-time Offense

 

N

%

%

%

%

TOTAL

23,996

67.4

16.9

11.5

4.2

Male

17,263

67.7

16.4

11.5

4.4

Female

  4,946

68.1

18.9

  9.2

3.8

Unknown

  1,787

63.2

16.6

17.5

2.6

 

X2 = 113.6, df = 6, p < .001

< 21 yrs

  2,642

78.7

  8.2

  7.5

5.6

21-24

  4,214

75.6

12.8

  6.1

5.6

25-34

  7,243

69.0

15.9

11.2

3.8

35-54

  8,780

59.2

21.9

15.5

3.4

> 55

  1,112

64.4

20.6

11.6

3.4

 

X2 = 805.4, df = 12, p < .001

Repeat Offense

 

N

%

%

%

%

TOTAL

9,666

51.6

21.0

22.7

4.7

Male

8,113

51.8

20.5

22.9

4.8

Female

1,341

50.8

24.5

21.3

3.4

Unknown

   212

47.2

20.3

24.1

8.5

 

X2 = 22.6, df = 6, p < .001

< 21 yrs

   390

70.0

14.4

11.8

3.8

21-24

1,376

63.8

18.5

12.9

4.9

25-34

3,654

53.4

19.1

22.9

4.7

35-54

3,922

44.1

23.8

27.5

4.6

> 55

   324

46.9

28.1

19.1

5.9

 

X 2= 274.4, df = 12, p < .001