1. Impact of legalized recreational marijuana in Washington State
Brianna Peterson, PhD, F-ABFT
Washington State Patrol
Toxicology Laboratory Division

2. History of marijuana in WA
Medical marijuana legalized in 1998
Removes state-level criminal penalties on the use, possession and cultivation of marijuana by patients who possess "valid documentation" from their physician affirming that he or she suffers from a debilitating condition and that the "potential benefits of the medical use of marijuana would likely outweigh the health risks."
No established state registration program

3. WA State Initiative-502
Public initiative; November 6, 2012 general ballot
Approved by popular vote (~56%)
Defined and legalized small amounts of marijuana and marijuana-infused products
Regulated marijuana production, distribution, and sale
DUI laws amended to include a per se level for blood THC
Possession by anyone <21 years, possession in larger amounts, & unlicensed/unregulated production of marijuana remains illegal

4. Driving Under the Influence (RCW 46.61.502/3)
(1) A person is guilty of driving while under the influence …     (b) The person has, within two hours after driving, a THC concentration of 5.00 or higher as shown by analysis of the person's blood … ; or     (c) While the person is under the influence of or affected by intoxicating liquor, marijuana, or any drug;
4(b) Analyses of blood samples obtained more than two hours after the alleged driving may be used as evidence that within two hours … a person had a THC concentration of 5.00 or more … and … above 0.00 may be used as evidence that a person was under the influence of or affected by marijuana …
(under 21 years): … has, within two hours … a THC concentration above 0.00

5. Toxicology testing in WA
Only one toxicology lab for entire state
Receive approximately 15,000 cases a year
Case types: Death investigation, DUI, DRE, sexual assault
39 counties
Testing is a free service funded by the state

6. Toxicology Testing All cases are tested for ethanol
All cases are screened for the following drug/drug class(es):
Amphetamines
Barbiturates
Benzodiazepines
Cannabinoids (cutoff for positive: carboxy THC at 10 ng/mL)
Cocaine metabolite
Methadone
Opiates
PCP
Tricyclic antidepressants
Enzyme Multiplied Immunoassay Technique

7. Total # DUI/DRE cases received
THC Results
Year
Total # DUI/DRE cases received
# of positive THC cases
% of positive THC cases
2009
4,809
877
18.2%
2010
5,012
974
19.4%
2011
5,132
1,036
20.2%
2012
5,298
988
18.6%
2013*
5,468
1,362
24.9%
2014
6,270
1,759
28.0%
2015
7,044
2,311
32.8%
2016 (Jan-April)
2,842
977
34.4%

8. Carboxy-THC Results 2009 4,809 1,267 26.3% 2010 5,012 1,413 28.2% 2011
Year
Total # DUI/DRE cases received
# of positive Carboxy-THC cases
% of positive Carboxy-THC cases
2009
4,809
1,267
26.3%
2010
5,012
1,413
28.2%
2011
5,132
1,460
28.4%
2012
5,298
1,515
28.6%
2013*
5,468
2,187
40.0%
2014
6,270
2,279
36.3%
2015
7,044
2,693
38.2%
2016 (Jan-April)
2,842
1,108
39.0%

9. Marijuana-related driving cases (%)

10. Demographics of marijuana positive cases
Year
Percent Male
Age, Range
Age, Median
2009
80 %
years
25 years
2010
78 %
years
2011
81 %
years
2012
77 %
years
2013
79 %
years
26 years
2014
15 – 74 years
2015
13 – 73 years
27 years

11. Summary of THC blood concentrations
Year
# cases positive for THC
THC concentration range
Average THC concentration
Median THC concentration
2011
1,036
1-58 ng/mL
6.4 ng/mL
4.8 ng/mL
2012
988
1-90 ng/mL
8.0 ng/mL
6.2 ng/mL
2013
1,362
2-77 ng/mL
7.2 ng/mL
5.2 ng/mL
2014
1,759
1-100 ng/mL
6.1 ng/mL
3.9 ng/mL
2015
2,311
1-69 ng/mL
5.7 ng/mL
3.8 ng/mL
2016 (Jan-April)
977
1-66 ng/mL
5.8 ng/mL
3.7 ng/mL

12. THC cases at or above 5 ng/mL
Year
# cases positive for THC
# cases positive for THC below 5 ng/mL
# cases (%) positive for THC above 5 ng/mL
2011
1,036
530
506 (49%)
2012
988
378
610 (62%)
2013
1,362
642
720 (53%)
2014
1,759
1,056
703 (40%)
2015
2,311
1,389
922 (40%)
2016 (Jan-April)
977
593
384 (39%)

13. Beyond the tox results

14. Missouri v. McNeely 2013 US Supreme Court decision
“Police must generally obtain a warrant before subjecting a drunken-driving suspect to a blood test”

15. Prosecutor’s perspective
Affected by cases easier to prove before I-502 passed
Since implementation things have gotten more difficult:
Under 5 ng/mL cases, prosecutors must review police video
Over 5 ng/mL cases usually involve more impairment so it is easier to charge on the affected by prong
Many DUI’s are dealt when under the per se level even with good signs of impairment and poor field sobriety tests
Exigent circumstances cases are usually thrown out
Increased ethanol and marijuana combined driving cases

16. Internal procedural changes
Normalize data in an attempt to eliminate effect of changes
Reporting limits
THC: changed from 1 to 2 ng/mL
Carboxy-THC: changed from 5 to 10 ng/mL
, often no EMIT/drug screen if blood alcohol > 0.10%
Exceptions: vehicular assault/homicide, drug specifically mentioned or requested, circumstances suggest drug use, DRE cases

17. Percentage of cases (BAC >0
Percentage of cases (BAC >0.10%) with EMIT positive results, Jan-Apr 2008, N=548
Unconfirmed EMIT results, however, conservatively decided to assume that 25% of untested high BAC cases ‘might’ be positive for cannabinoids
25% of cases with BAC > 0.10% were removed from 2013 dataset

18. Data interpretation
Reliable information regarding traffic accidents and traffic deaths to correlate with toxicology results
Information regarding time course of incident: time of stop and time of blood draw.
THC has a short half life
Uncertainty of Measurement
26% for THC at k=3 (99.7% confidence)
Result of 6.7 ng/mL is reported at 6.7 ± 1.7 ng/mL

19. Things to remember Establish a reliable baseline of data
Benefit of having years of comparison data
Be aware of any changes in testing practices
Lower limit of reporting
Increasing number of cases tested
Be aware of what is scope of data
Regional – different labs testing, different reporting guidelines, different uncertainty measurements
Are all cases being screened for marijuana use?

20. Brianna.peterson@wsp.wa.gov 206-262-6100
Questions?