Investigations | Section 4.4

Fundamentals of Criminal Investigations

Adam J. McKee, Ph.D.

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Section 4.4: Drug & Chemical Evidence

Perhaps the most diverse classification of forensic science is forensic chemistry.  Forensic chemists are called upon to analyze many different classifications of evidence, some of which have already been discussed in this book (e.g., paints and soils).   In this section, we will focus on drugs and gunshot residue.

Drug Evidence

The scientists in the chemistry section of the crime lab analyze items of evidence submitted by law enforcement for the presence or absence of controlled substances.  Drug evidence may be in the form of plant material (such as marijuana, synthetic cannabinoids, salvia, and khat), solids (such as methamphetamine, powder cocaine, crack cocaine, and pharmaceutical or clandestine tablets), liquids (such as clandestine laboratory samples), or paraphernalia (such as smoking devices, straws, or spoons).

When evidence is submitted to the lab, an initial physical examination is performed.  This physical examination includes examining packaging for seals and a macroscopic examination of the evidence.  After initial observations are noted (including a weight, volume and/or unit count), a drug chemist typically screens the evidence using chemical spot tests and/or instrumentation.  After screening, the scientists use a variety of extractions and instrumentation to confirm the presence or absence of controlled substances as indicated by the preliminary screening tests.  Once all examinations are completed, a report is written.

Reports routinely include an amount determination (such as grams, milliliters or units) and a qualitative identification of any controlled substances identified. The lab may also perform quantitative examinations to determine the concentration of the controlled substance.

Some state and local forensic laboratories perform quantitative (or purity) analyses, but the majority do so only under special circumstances, such as a special request from law enforcement or from the prosecutor. A smaller number of laboratories perform quantitative analysis on a more routine basis due to state laws that require the amount of pure heroin or cocaine in an item to be determined.

Forensic chemists also provide expert testimony in both state and federal courts.  These drug chemists are also a resource for controlled substance information for the courts and other state agencies.

National Forensic Laboratory Information System (NFLIS)

NFLIS represents a partnership that includes 263 federal, state, and local forensic laboratories. The information collected through NFLIS supports DEA’s mission to enforce the controlled substances laws and regulations of the United States, including tracking the diversion of controlled pharmaceuticals and the diversion of controlled chemicals into illegal markets.

NFLIS provides a unique source of information on the nation’s drug problem, providing detailed and timely information on substances secured in law enforcement operations across the country. The NFLIS 2005 Annual Report presents national and regional findings on drug cases analyzed during the past year, including city- and county-level results on drug seizure locations. Among the key findings presented in the NFLIS 2005 Annual Report:

  • An estimated 1.7 million drug items were analyzed by state and local laboratories in the United States in 2005. Cannabis/THC was the most frequently identified drug (573,904 items), followed by cocaine (570,176), methamphetamine (247,288), and heroin (87,402).
  • Nationally, cannabis/THC, heroin, and MDMA declined significantly from 2001 to 2005, while methamphetamine, oxycodone, and hydrocodone items increased significantly.
  • Regionally, methamphetamine increased significantly in the South, more than doubling over the 5-year period, while cocaine and heroin declined. Methamphetamine also increased in the Northeast, while heroin declined.
  • Among other drugs in the top 25, oxycodone, hydrocodone, and alprazolam, all available in pharmaceutical products, increased significantly in the Northeast between 2001 and 2005. In addition, oxycodone increased in the West and Midwest, hydrocodone increased in the South and Midwest, and alprazolam increased in the Midwest.
  • Overall, hydrocodone (39%) and oxycodone (30%) accounted for more than two-thirds of all identified narcotic analgesics, while alprazolam (e.g., Xanax) accounted for 61% of reported benzodiazepines and MDMA accounted for 84% of reported club drugs

Drug Categories

The NFLIS also provides a helpful system of organizing illicit drugs into related categories.  Interestingly, the degree to which these different “families” of drugs are found varies substantially by region.  

Narcotic analgesics are pain relievers available by prescription. According to the 2005 National Survey on Drug Use and Health (NSDUH), approximately 5% of persons aged 12 or older, or 11.8 million, used pain relievers in the past year for non-medical reasons. Among adolescents aged 12 to 17, an estimated 7%, or 1.7 million, reported such use during the past year. A total of 51,432 narcotic analgesics were identified by NFLIS laboratories in 2005, representing nearly 4% of all items analyzed (Table 2.1). Hydrocodone (39%) and oxycodone (30%) accounted for the majority of all narcotic analgesics reported. The following drugs made up more than one-quarter of narcotic analgesics: methadone (11%), morphine (6%), codeine (5%), propoxyphene (3%), dihydrocodeine (2%), and hydromorphone (2%).

Benzodiazepines are used therapeutically to produce sedation, induce sleep, relieve anxiety and muscle spasms, and prevent seizures. Benzodiazepine abuse is often associated with young adults and adolescents who take benzodiazepines to get “high.”2 During 2005, a little more than 2% of all analyzed drugs, or 33,834 items, were identified as benzodiazepines in NFLIS (Table 2.2). Alprazolam (e.g., Xanax) accounted for 61% of reported benzodiazepines. Approximately 17% of benzodiazepines were identified as diazepam, and 16% were identified as clonazepam.

Club drugs.  MDMA, ketamine, and GHB/GBL are the most common club drugs. The abuse of MDMA, also known as Ecstasy, has declined in recent years. However, according to the 2005 Monitoring the Future Survey, an estimated 5% of 12th grade, 4% of 10th grade, and 3% of 8th grade students used MDMA during their lifetimes.3 In NFLIS, 12,473 club drugs were identified in 2005 (Table 2.3). Of these, 84% were identified as MDMA. Among the other club drugs reported, 9% were identified as MDA, 4% as ketamine, and 3% as GHB/GBL. MDMA constitutes the highest percentages for each region, representing 87% of club drugs in the West, 87% in the Midwest, 86% in the South, and 65% in the Northeast. The Northeast continues to report the highest percentages of MDA (19%) and ketamine (14%).

While anabolic steroids are legally available in the United States by prescription, many users obtain the steroids illegally through production in clandestine laboratories, smuggling from other countries, or diversion from U.S. pharmacies. The 2005 Monitoring the Future Study shows a significant decline in past year steroid use among 12th grade students, from 2.5% in 2004 to 1.5% in 2005. However, past year steroid use remained relatively the same from 2004 to 2005 among 8th and 10th grade students.3 During 2005, a total of 1,728 items were identified as anabolic steroids (Table 2.4). In NFLIS, the most commonly identified anabolic steroid was testosterone (38%), followed by methandrostenolone (17%), nandrolone (13%), and stenozolol (12%). Approximately 44% of items in the Midwest and South, 31% in the West, and 28% in the Northeast were identified as testosterone (Figure 2.4). Slightly less than one-fifth of items across all census regions were identified as methandrostenolone.  

Stimulants.  Methamphetamine is a highly addictive stimulant. The number of methamphetamine laboratories seized by law enforcement agencies increased by 25% between 2001 and 2004.  Stimulants, including methamphetamine and amphetamine, were involved in 42,538 emergency department (ED) visits, accounting for about 7% of all drug-related ED visits during the last two quarters of 2003.5 A total of 230,769 stimulants were identified in NFLIS during 2005, accounting for about 16% of all items reported. An estimated 97% of stimulants, or 224,605 items, were identified as methamphetamine. An additional 2,888 items were identified as amphetamine, and 1,468 as methylphenidate. Methamphetamine accounted for more than 9 out of 10 stimulants reported in the West, Midwest, and South, and for almost 6 out of 10 stimulants reported in the Northeast. In the Northeast, 24% of stimulants were reported as amphetamine and 12% as methylphenidate.

Drug Combinations.  Taking multiple drugs simultaneously or mixing substances can be deadly. The typical drug misuse death reported as part of the 2003 Drug Abuse Warning Network (DAWN) involved two or more drugs. Cocaine with opiates/opioids was the most common illicit drug combination involving death.6 During 2005, 19,560 items identified in NFLIS, about 1% of all reported items, contained two or more substances. The five most common combinations in 2005— cannabis/THC and cocaine (8%), methamphetamine and MDMA (7%), cocaine and heroin (7%), methamphetamine and dimethylsulfone (6%), and methamphetamine and ephedrine / pseudoephedrine (4%)—accounted for nearly one-third of all combinations reported.

Cocaine, including powder and crack cocaine, was present in 24% of all drug combinations reported during 2005. The most common cocaine combination contained cannabis/ THC (8%). Cocaine/heroin, which is often referred to as a “speedball,”represented nearly 7% of cocaine combinations, and cocaine/methamphetamine represented about 3%. Many of the other cocaine-related combinations included excipients used to dilute cocaine. These included non-controlled substances such as procaine (a local anesthetic), inositol, caffeine, boric acid, benzocaine, and lactose.

Heroin was present in 15% of all drug combinations, or 2,899 items, reported in 2005.  Almost one-half of the heroin combinations were reported as heroin/cocaine. Among the other substances combined with heroin, many were excipients designed to dilute or adulterate heroin, including procaine, caffeine, mannitol, lidocaine, inositol, and lactose.

Methamphetamine was present in a total of 6,012 items, or in about 31% of all drug combinations. Methamphetamine/MDMA (1,446 items), methamphetamine/ dimethylsulfone (1,131 items), methamphetamine/ephedrine or pseudoephedrine (752 items), methamphetamine/cocaine (577 items), and methamphetamine/cannabis (548 items) were the most commonly reported combinations. MDMA was reported in 7% of methamphetamine combinations, up from 5% in 2004.

Hair Toxicology

Forensic testing for drugs of abuse in hair has become a useful diagnostic tool in determining recent past drug use as well as examining long-term drug history through segmental analysis (i.e. identification and quantification of drugs along the length of the hair shaft from scalp hair). The usefulness and the importance of hair analysis depends on the ability to identify and quantify drugs and metabolites in hair that arise from ingestion but not from passive exposure or exogenous application of drugs.

Hair has many beneficial aspects when compared to urine and blood. Since sample collection is non-invasive, hair analysis is commonly used in workplace drug testing and drug treatment programs. Provided the hair has not been cut, it may be easy to obtain a second sample if the results are inconclusive or challengeable. It can be used for establishing personal drug history in situations where classical matrices are not available such as in putrefied bodies; when the full drug use history is unknown; or when time is a factor, for example in drug facilitated sexual offense (DFSA).

Hair analysis can also assist in drug compliance testing and drug abstinence monitoring. Moreover, drug-hair analysis is becoming a popular alternative to urinalysis since urine samples provide only short-term information about drug use while hair samples provide a larger window of detection as well as history of use over time. This is because head hair grows at an average rate of 1 cm per month and hence preserves the drug use history of an individual along its length. Due to the cosmetic treatment of an individual, the drugs could be degraded however not fully eliminated. Therefore cosmetic history of a person must be considered in such cases while interpreting hair analysis results.

Gunshot Residue

Gunshot residue (GSR) collection kit or GSR collection stubs; paper envelopes; paper towels; clean paper; waterproof pen; evidence tape; powder-free protective gloves; face protection. Determine if the suspect(s), victim(s), or witness(es) should be tested; collect the GSR as soon as possible. Do NOT use tape lifts in place of a GSR kit stub. The instructions included in the GSR kit should always be followed. Sample the hands for GSR using the collection kit as soon as possible. If collection cannot be made immediately on contact with the subject, individually bag the subject’s hands using paper bags and not plastic bags (as plastic may cause hands to sweat). Good GSR samples can generally be obtained from the web portions of the hands.

GSR collection kits should contain materials (e.g., carbon-coated adhesive stubs or adhesive-coated discs) required to perform scanning electron microscopy (SEM) residue tests. Do not use GSR kits that have swabs or color tests. Do not allow the suspect(s), victim(s), or witness(es) to wash their hands or subject the hands to any liquids after the shooting, or any rubbing onto other surfaces (e.g., clothing, bag on hand, furniture, etc.). Keep GSR kits away from firearms evidence. Evidence such as vehicles can also be tested for the presence of GSR, by using the same procedure as would be used on hands.

Key Terms

References and Further Reading


Gautam, L. & Cole, M. D. (2013).  Hair Analysis in Forensic Toxicology.  Forensic Magazine.  Available:



Modification History

File Created:  05/02/2019

Last Modified:  05/16/2019

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This work is licensed under an Open Educational Resource-Quality Master Source (OER-QMS) License.

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