1. Drug Identification
In what types of situations would a forensic scientist need to test for drugs?
In what ways can forensic scientists test for drugs? (What types of biological samples would they use to test for drugs?)

2. Most common drug tests Urine drug test (urinalysis)
Test card is used on site for immediate results, or sample is sent away to a lab to be tested with a sophisticated gas analyzer.
To prevent substitution of another person's urine or an adulterating substance, one is sometimes observed while urinating. While some people attempt to defeat a urine test by drinking copious amounts of water, a sufficiently diluted sample may be rejected.
Some herbal extracts are marketed for "detox" of controlled substances from one's urine, but their efficacy is controversial.

3. Most common drug tests Hair Follicle drug test
Hair testing is quite accurate
Can go back 6 months (timeline!)
Many people try to get around this by just shaving their heads.
This is ineffective, as hair from one's underarm, pubic, leg or arm hair can also be used.

4. Most common drug tests Blood drug test
Blood testing is usually performed for serious employment positions or by insurance companies. This is expensive and not very common.
Toxicologists can use blood samples to analyze overdoses or poisonings.

5. Most common drug tests Saliva drug test
This is not common and can only detect toxins used 3-4 days prior. Insurance companies and law enforcement agencies use this method most often.

6. Drug Identification
The challenge or difficulty of forensic drug identification comes in selecting analytical procedures that will ensure a specific identification of a drug.
This plan, or scheme of analysis, is divided into two phases.
Screening (Presumptive) test: ?
Confirmation test: a single test that specifically identifies a substance.

7. Screening Tests
Screening (Presumptive) Tests:
Why use them?

8. Preliminary Analysis
The unknown substance may be any one of a thousand or more commonly encountered drugs.
Screening tests reduce these possibilities to a small and manageable number.
A series of color tests that will produce characteristic colors for the more commonly encountered illicit drugs.

9. Duquenois-Levine Test
Type of Test
Chemicals
What the Results Mean 
Marquis Color
Formaldehyde and concentrated sulfuric acid 
Heroin, morphine and most opium-based drugs will turn the solution purple. Amphetamines will turn it orange-brown. 
Cobalt thiocyanate
Cobalt thiocyanate, distilled water, glycerin, hydrochloric acid, chloroform 
Cocaine will turn the liquid blue. 
Dillie-Koppanyi
Cobalt acetate and isopropylamine 
Barbiturates will turn the solution violet-blue. 
VanUrk
P-dimethylaminobenzaldehyde, hydrochloric acid, ethyl alcohol 
LSD will turn the solution blue-purple. 
Duquenois-Levine Test
Vanillin, acetaldehyde, ethyl alcohol, chloroform 
Marijuana will turn the solution purple. 

10. Preliminary Analysis Microcrystalline tests:
Analyze the size and shape of crystals formed when the drug is mixed with specific reagents.
Fig. 3. Microcrystalline response of selected psychoactive stimulants tested with mercury chloride as reagent (a) BZP, (b) caffeine, (c) d-amphetamine, (d) dl-amphetamine, (e) ephedrine hydrochloride, (f) ephedrine sulphate, (g) MDAI freebase, (h) mephedrone, (i) methamphetamine. Note: (a) was taken at 76× magnifications, images (b)–(i) were taken at 19× magnifications.

11. Conformational Determination
Once this preliminary analysis is completed, a confirmational determination is pursued.
Forensic chemists will employ a specific test to identify a drug substance to the exclusion of all other known chemical substances.
Typically infrared spectrophotometry or gas chromatography-mass spectrometry is used to specifically identify a drug substance.