Drug Analysis (Chemistry)
Forensic drug chemistry undoubtedly holds substantial value in the growing world of forensics. Drug chemists, also known as criminalists, at the Sacramento County Crime Lab analyze evidence submitted by law enforcement agencies for the presence or absence of controlled substances. Law enforcement and the Sacramento County District Attorney’s Office can seek criminal charges while the court system can determine proper sentencing based on the examination results. Therefore, drug criminalists can be called as expert witnesses in the event a court case goes to trial. It is important to note that all drug criminalists at the Sacramento County Crime Lab possess the basic requirements outlined by the county to be qualified for analysis and testimony; most exceed those qualifications!
Although forensic drug chemistry performed in accredited labs across the country may follow the same procedures, the types of drug evidence submitted can differ widely from lab to lab. Due to an ever-changing drug culture, different social demographics, and regional location of the lab, certain drugs are more commonly seen. In the county of Sacramento, common types of drug evidence submitted may be, but are not limited to, crystalline material (like methamphetamine), plant material (like marijuana, synthetic cannabinoids, and mushrooms), solid material (like black-tar heroin and crack “rock” cocaine), tablets (like pharmaceutical or clandestine opiates or anti-anxiety medication), liquid material (like heroin in a syringe or a ‘date rape drug’ in a liquid solution), or objects that drugs could be adhered to (like straws, pipes, syringes, and paper material).
The basic roadmap for any unknown drug evidence begins with submission to the evidence unit conveniently located at the front of the lab. Here, designated law enforcement personnel create a chain of custody with the crime lab and the evidence is given a unique barcode label for each item submitted. The evidence from each case is then stored at the lab in a locked vault to await testing. When a drug criminalist is assigned a case, the evidence unit staff transfers the evidence to the criminalist using a barcode scanner to scan the criminalist’s badge and the barcode on the evidence. This creates an internal, digital footprint of when evidence was relinquished and to whom. The evidence is then stored in a locked storage area in the Drug Chemistry unit. Next, cases are prioritized by their upcoming court date and the examination process begins.
There are three types of examinations that occur in sequential order to determine the presence or absence of controlled substances: physical, presumptive, and confirmatory examinations. Initially, a physical examination is performed by noting the physical characteristics of the evidence such as the powder, crystalline, liquid, or solid form. Attributes like the color and manner in which the item is packaged is also noted. Additionally, the weight, volume, or unit count is recorded. In rare cases, the amount of sample submitted is very minimal, like residue. It is very important for the criminalist to use the least amount of sample for all steps in the testing process because it may need to be re-tested or analyzed by an outside laboratory.
After the physical examination, a presumptive chemical test is performed. A very small amount of sample is placed on a spot plate and tested with different chemicals that change colors based on the chemical properties of that sample. All color changes, or lack thereof, are recorded. Color tests are presumptive, not confirmatory, because they only determine if a chemical reaction occurred or not.
Based on the results of the presumptive color tests on a sample, the criminalist will decide whether it is necessary to perform an extraction and what extraction method to use. If the criminalist does decide to extract the suspected drug, they will usually utilize the gas chromatography/mass spectrometry (GC/MS) technique as a confirmatory test. Different drugs extract better in certain extraction methods because of their chemical properties. For example, some drugs are more acidic or basic in nature, making them more sensitive to certain pH extraction methods. The four types of extraction methods used in the lab are: acid extraction, base extraction, pH 9 extraction, and solvent dissolution. Acidic drugs can be readily extracted with an acid extraction while basic drugs can be readily extracted with a basic extraction. Certain drugs such as morphine are extracted best at a pH of 9, while the best method of extraction for other drugs would be to dissolve them in solvents they are compatible with.
Once the suspected drug is extracted and placed in a GC/MS sample vial, the sample is placed on the GC/MS instrument to be analyzed. GC/MS is a two-part technique that provides identification based on the concept that all compounds have unique combinations of retention time and molecular fragmentation pattern. GC is the portion that separates a mixture into its individual components; MS is the portion that identifies the compound by producing a mass spectrum (or a molecular fingerprint) that is then compared to known standards.
Certain drugs do not necessarily need to be extracted to be analyzed, and with those drugs the criminalist may choose to use fourier-transform infrared spectroscopy (FT-IR) as a confirmatory test. FT-IR is a technique used to obtain infrared spectrum of infrared light being absorbed and being passed through a compound. Similar to the GC/MS mass spectrum, an IR spectrum is generated and compared to known standards. FT-IR spectroscopy is useful because chemical structures vibrate uniquely when absorbing infrared radiation, creating a unique IR spectrum.
After performing a confirmation test (GC/MS and/or FT-IR), the criminalist will take the data and compile a report with their findings. Once the criminalist finishes a report, they will turn it in for technical and administrative review done by the criminalist’s own peers in their unit. A technical review is done to ensure that the procedures the criminalist followed and the results they obtained were technically sound and accurate. An administrative review is done to catch administrative faults such as misspellings or grammatical errors. Once the review process has concluded, the report can then be released to the agency that requested it. Afterwards, the criminalist will then re-package the suspected drugs and send them back to the evidence unit where the corresponding agency can pick them back up. Weeks or months later, the criminalist may be called as an expert witness to testify to the results in these reports.