Evaluation of Drug Recognition Expert Reports in Marijuana Cases

Brianna Peterson, Ph.D. and Rod Gullberg, M.S.Washington State Patrol

September 20, 2011

Goal of study

• Determine if DRE indicators for cannabis are present in cases with THC detected

• Compare indicators for subjects with active THC versus THC-COOH only

size

HorizontalGaze Nystagmus

VerticalGazeNystagmus

Lack ofConvergence

Pupil

Reactionto light

Pulse

BloodPressure

Body Temp

Depressants Inhalants DissociativeAnesthetics

Stimulants Hallucinogens NarcoticAnalgesics

Cannabis

Present Present Present None None None

Present Present Present None None None

Present Present Present None None None

Normal Normal Normal Dilated Dilated Constricted

Slow Slow Normal Slow Normal Little to none

Down Up Up Up Up Down

Down Up/Down Up Up Up Down

Normal Up/Down/Normal

Up

None

None

Present

Dilated

Normal

Up

Up

Normal Up Up Down

DRE Matrix

DRE indicators for cannabis category

• Lack of convergence (LOC) present• Pupil size normal to dilated• Elevated pulse rate• Elevated blood pressure

• Horizontal gaze nystagmus (HGN) not present• Vertical nystagmus (VGN) not present• Reaction to light is normal• Body temperature is normal

THC pharmacokinetics

• Highly lipid soluble

• Short half-life– 3 hrs post smoking, THC in serum <5 ng/mL

• Main metabolite: 11-nor-9 carboxy-THC (THC-COOH)

Methodology• DRE cases from 2007-2009; blood sample

analyzed• Tested for volatiles by Headspace Gas

Chromatography• EMIT drug screen

– Cannabinoids cut off = 10 ng/mL THC-COOH

• THC confirmation by GC/MS (SIM mode)– Limits of Detection

• THC = 1.0 ng/mL• THC-COOH = 5.0 ng/mL

Cases that were only positive for THC or THC-COOH

Subjects• THC/THC-COOH (n=101)

– 93% male– 78% Caucasian– Average age: 24 (range: 16-70)

• THC-COOH only (n=147)– 79% male– 84% Caucasian– Average age: 27 (range: 14-61)

• Not impaired (n=17)– 76% male– 94% caucasian– Average age: 38 (range: 19-74)

147 THC/THC-COOH cases

5 10 15 20 30 60 90 120 150 180 210More0

20

40

60

THC-COOH concentration

ng/mL

Fre

qu

ency

Mean = 74.1; median = 61.7

1 2 3 4 5 10 20 30 More0

20

40

60

THC concentration

ng/mL

Fre

qu

ency

Mean = 7.3; median = 5.7

101 THC-COOH only cases

5 10 15 20 30 60 90 120 150 180 210More0

1020

3040

THC-COOH concentration

ng/mL

Fre

qu

ency

Mean = 16.6; median = 13.5

Results

Lack of convergence

*p=0.003*p=0.003

0

10

20

30

40

50

60

70

YesNo

THC/THC-COOH

Pe

rce

nta

ge

THC-COOH

*

*p=0.003

Normal range: 2.5 – 5.0 mm

Average pupil size: Room light

0 10 20 30 40 50 60 70 80 900

1

2

3

4

5

6

7

8

9

10

THC/THC-COOH

THC-COOH

ng/mL

56%, 61% above normal range

Average pupil size: Dark

Normal range: 5.0 - 8.5 mm

0 10 20 30 40 50 60 70 80 900

1

2

3

4

5

6

7

8

9

10

THC/THC-COOH

THC-COOH

ng/mL

60%, 58% above normal range

0 10 20 30 40 50 60 70 80 900

1

2

3

4

5

6

7

8

9

10

THC/THC-COOHTHC-COOH

ng/mL

Average pupil size: Direct light

49%, 47% above normal range

Normal range: 2.0 – 4.5 mm

0 10 20 30 40 50 60 70 8040

50

60

70

80

90

100

110

120

130

140

150

THC/THC-COOHTHC-COOH

ng/mL

Average pulseNormal range = 60-90 bpm

57% above normal range

Systolic blood pressure

0 10 20 30 40 50 60 70 8080

90

100

110

120

130

140

150

160

170

180

190

200

THC/THC-COOHTHC-COOH

ng/mL

Normal range = 120 – 140 mm Hg

45% above normal range

Body Temperature

Normal range = 98.6 ± 1°F

0 10 20 30 40 50 60 70 8095

95.4

95.8

96.2

96.6

97

97.4

97.8

98.2

98.6

99

99.4

99.8

100.2

100.6

101

THC/THC-COOHTHC-COOH

ng/mL

73, 87% in normal range

Not impaired: 17 cases from 2007 - 2009

Summary

Cannabisindicator

THC/THC-COOH

THC-COOH

Not impaired

HGN None 9% 11% 6%

VGN None 0 2% 0

Lack of convergence Present 66% 47% 6%

Pupil Size Normal to dilated

55% 55% 15%

Reaction to light Normal 76% 77% 82%

Pulse Elevated 57% 57% 25%

Blood pressure(Systolic/diastolic)

Elevated 45%/22% 45%/25% 41%/12%

Body Temperature Normal 73% 87% 77%

Summary

THC/THC-COOH

THC-COOH

Bloodshot eyes

Eyelid tremors

2/8 clues on WAT

2/4 clues on OLS

Not impaired

86% 81% 24%

81% 81% 38%

72% 81% 25%

46% 57% 31%

Other indicators

• Romberg test: estimation of 30 seconds– Normal range = 25 to 35 seconds

THC/THC-COOH THC-COOH Not impaired

60% 51% 47%

Other indicators

• Rebound Dilation

• Reaction to light– Normal, slow, little

THC/THC-COOH THC-COOH Not impaired

43% 41% 6%

THC/THC-COOH THC-COOH Not impaired

77% 76% 82%

DRE Opinion

• THC/THC-COOH cases– 97% DRE called cannabis

• Other cases called ‘not impaired’

– 98% subject admitted to marijuana use• THC-COOH only cases

– 97% DRE called cannabis• Stimulant/not impaired

– 88% subject admitted to marijuana use

Conclusions

• DRE matrix is useful tool for predicting marijuana use

• Similar indicators for THC/THC-COOH and THC-COOH cases– Short half-life, long exam process

Beasley et al. study

• Examined which indicators best predict substance (n =742)

• Stimulants versus cannabis– Stimulants: less reddening of eyes and

rebound dilation, more likely to have hippus, injection sites, slow reaction to light

– Cannabis: more likely to have lack of convergence

Toward a More Parsimonious Approach to Drug Recognition Expert Evaluations. Traffic Injury Prevention 2009;10:513-518

Acknowledgments

• Rod Gullberg– Research Analyst, Washington State Patrol