Drug Identification in Law Enforcement
Written by Prasant Potuluri, PhD   

A significant portion of drug policing efforts have focused on large-scale seizures, with the objective of halting the flow of product from its origin or at entry into other countries. In practical terms, however, it is the mid- to low-level trafficker who has a more negative impact on the community. With budget cutbacks, police are forced to consider the cost of enforcement when choosing which crimes to prosecute, and lab testing is expensive. Meanwhile, significant backlogs at labs result in cases that are not prosecuted in a reasonable timeframe, or are dismissed.

Fortunately new field-portable instruments promise to put more sophisticated drug identification in the hands of first responders. Accurate field-testing can be used for preliminary hearings and charging, and more importantly, may facilitate a rapid plea agreement. As field screening improves, the demand for confirmatory identification on crime labs can decrease, allowing cases to be processed more quickly.

Traditional drug identification methods

When suspected illegal substances are encountered in the field, colorimetric testing is performed. This identifies the most likely class of compound (amphetamine, cocaine, etc.), but is prone to subjective results and false positives. Since each tests for a specific drug class, several attempts may be needed to classify a single sample. Available for fewer than two dozen drugs, the tests have limited shelf life and expose officers to potential contact with chemicals and broken glass.

Evidence law then requires testing in an accredited lab using two to three independent techniques. HPLC (high performance liquid chromatography) moves the sample through a column via liquid pressure, with each chemical component moving at a different speed and detected in turn. Gas chromatography (GC) does the same, but with the sample vaporized and moved by a carrier gas. These techniques can be combined with more sophisticated detection like mass spectrometry (MS) or flame ionization detection (FID) to identify and quantify several compounds in the same sample. HPLC is the favored method for quantification of morphine and opium samples, while LC-MS seems to be best for benzodiazepines. GC-MS is probably the most widely used, but is unable to identify cutting agents.

An alternative to separation of a sample is to look at the structure of its molecules via spectroscopy. Fourier transform infrared spectroscopy (FTIR) and infrared (IR) spectroscopy do so using infrared light, and Raman spectroscopy probes chemical bonds indirectly by scattering laser light off the sample. The spectral fingerprint created is then compared to a library for positive identification. FTIR is often used to identify cocaine and is widely used for amphetamines, but is not well suited to aqueous samples or barbiturates and benzodiazepines. Raman spectroscopy, however, is not sensitive to water. Compared to IR or FTIR, Raman spectra typically have fewer and narrower peaks, making it easier to resolve the compounds in a mixture. It is non-contact, allowing samples to be measured through plastic bags or glass vials, preserving the original sample.

Emergence of field instruments

The Mobile Field Lab-3000 from Centice is one example of a field-portable drug-screening system that utilizes Raman spectroscopy. By deploying the capability for chemical analysis into the field, law enforcement agencies can reduce the pressure on forensic laboratories for confirmatory identification.

The need for better screening in the field has led to the development of ruggedized GC-MS and FTIR instruments, as well as handheld Raman systems. Portable benchtop GC-MS units perform well, but require a technical operator, warmup time, and sample preparation. Person-portable units are faster and easier to use, but scan a more limited mass range. All cost $75,000 or more. A portable FTIR unit can be less expensive, with performance equal to a lab instrument, but still requires warmup time and a small amount of the sample.

When trace amounts or residues need to be analyzed in the field at border crossings or for vehicle inspection, ion mobility spectrometry (IMS) systems offer presumptive testing of particulate introduced to the instrument via a surface wipe. Though low-cost and easy to operate, some household items can act as distractors (green tea vs. cocaine), or overlap (THC and heroin). Systems exist for vapor detection as well, but canines still remain state of the art.

The strongest new contender in field-portable screening systems is Raman. Commercially available field-portable Raman devices include the Mobile Field Lab-3000 (manufactured by Centice) and TruNarc Handheld Narcotics Analyzer (manufactured by Thermo Scientific).

One of the biggest trends is toward synthetic or “designer” drugs, including amphetamine-type substances, “bath salts”, and synthetic cannabinoids (“spice”). Their widely ranging chemical compositions make it challenging for the law to keep up with new variants, both in terms of legislation and identification. Raman adapts particularly well to the challenge of emerging drugs. Each compound or mixture scanned has a unique spectral fingerprint that can be added to the library as it is encountered, allowing comparison to another unknown substance within minutes. This type of detailed comparison can be used to identify drugs by batch, and to link distribution. Combined with the ability to identify precursors and essential chemicals, Raman offers first responders the kind of forensic intelligence needed to act quickly and decisively.

The technique still needs to be approved by prosecutors and judges, but at a price tag of $14-20,000 and no need for technical expertise to operate, it offers low cost per use. As adaptable as it is for new compounds, the technique is not suited to substances with inherently weak Raman signals (heroin) or high fluorescence (cannabis). It performs well for cocaine, distinguishing salt from base forms. It can also distinguish easily between date rape drugs like GHB, rohypnol, and diazepam. More than one component in a mixture can be identified by subtracting the best match and resubmitting the fingerprint to the library for comparison. The best match, however, may not be the major component in the sample; it may be the particular particle on which the Raman laser is focused, or have a stronger Raman signal. Still, when compared to colorimetric tests by those working in the field, the overwhelming opinion is that it makes identifying drugs easier, less dangerous, and less expensive.

Raman spectroscopy in the field

Commander Phillip W. Price with Georgia’s Cherokee Multi-Agency Narcotics Squad (CMANS) has been using one of the portable Raman technologies, the Mobile Field Lab-3000, for controlled prescription drug (CPD) identification for more than a year and a half.

“The MFL-3000 is an excellent tool that gives us a greater deal of confidence than we had in the past when it comes to presumptive drug testing. It provides a refined test that is as close as you can get to 100 percent without having all the checks and balances,” stated Price.

In the past, Poison Control was called and CPDs were identified by appearance (markings, color, and size). With Raman spectroscopy, substances are identified by chemical analysis. That means crushed and partial pills as well as tablets with the markings removed are easily identified in a matter of seconds.

“As the technology evolves and the hardware is refined, these tools have the potential to become standard in the field. We are in the early adoption phase and there are a multitude of other uses (beyond narcotics identification) such as in HAZMAT incidents,” Price added.


The unique advantages of field-portable Raman to speed the screening and prioritizing of evidence has the potential to streamline and reduce the cost of low-level drug prosecution, making it a key component in the strategy to fight the trafficking of drugs in our communities.

About the Author

Dr. Prasant Potuluri is CEO and co-founder of Centice. He has been instrumental in creating multiple products from the company’s Raman spectroscopy and coded aperture spectroscopy technologies. He has published articles in scientific journals and presented at numerous conferences and trade shows including law enforcement and drug task force meetings. His PhD work on compressive sampling was the first demonstration of a concept that is now an actively pursued topic of interest by DOD and DHS in their next generation of explosive detection sensors.

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