The commercially available colorimetric test kit called NIK® test is used by law enforcement and in the correctional system, but has received criticism due to the possibility of false positives.1,2 Police officers use the test to determine probable cause for an arrest, but NIK® has been criticized in multiple instances when people were arrested based on false positives.3
The NIK® test is commercially available from the Safariland Group, and is one type of colorimetric test that is sold as a presumptive color test5,6 for the identification of marijuana, cocaine, opiates and amphetamine-type compounds like methamphetamine, Ecstasy, Rohypnol, and Methylphenidate. Figure 1 shows the NIK® Master-PacTM, a case containing NIK® Tests A, B, F, I, G, J, K, L, O, R, T, U and W.
These are the commonly used tests for abused narcotics, and each box contains 10 tests, each in a plastic pouch. Depending on the test, each pouch contains 1 to 3 ampoules holding the chemicals used in the test. The ampoules are broken consecutively from left to right with intermittent shaking from ampoule to ampoule, and any color changes observed.
The NIK® test is accompanied by an IDENTIDRUGTM chart (Figure 1) for use with the polytesting system, as well as a training CD and a PowerPoint presentation Safariland. The Group also provides a test for law enforcement officers who can submit their answers to the Safariland Group and receive a scored accreditation as a NIK® user. Some narcotics are tested with a cascade of tests referred to as “polytesting” to narrow down the analyte identity.
Figure 1: The commercially available NIK Master-PacTM in a carry case that is used for the presumptive identification of abused narcotics. The IDENTIDRUGTM Chart shows the polytesting sequence that needs to be performed to narrow down the identity of the unknown substance
Drugs tested with this system include opioids, amphetamines, cocaine, and more. As seen at the top center of the chart, the system is designed so Test A is always first, and then depending on either the color change or lack thereof, ensuing tests hone in on the analyte identity. As seen in Figure 2 for cocaine testing, Test A (Marquis test) should yield no color change, which then leads to the right on the IDENTIDRUGTM chart to Test G (Modified Scott test). Test G resulting in a biphasic mixture with the top layer pink and the bottom layer bluegives a positive presumptive test for cocaine. At this point, law enforcement would then send the sample to the crime lab for positive identification/confirmation using either GCMS or LCMS (Gas Chromatography/Mass Spectrometry or Liquid Chromatography/Mass Spectrometry).
The NIK® system does have stand-alone tests, as shown in the blue boxes at the bottom of the chart: Test E (Marijuana, Hashish, THC), Test M (Methaqualone), Test N (Talwin & Pentazocine), Test P (Propoxyphene), and Test Q (Ephedrine). All of the NIK® tests are designed for testing solids, but liquids may be tested by first absorbing the liquid onto white paper, drying, and then loading the paper into the test pouch.
Figure 2: From left to right,NIK-A and NIK-G
straight out of the box. and then NIK-A after testing cocaine giving a colorless solution so no color change, and then NIK-G after
testing cocaine to give pink layer over blue layer, resulting in a positive presumptive test for cocaine
The NIK® test was studied in our laboratories, and we determined that there are several advantages and disadvantages of the test.Positive aspects include ease of use and the quick turnaround time for the results. Negative points include the probability of using the incorrect sample size and the subjective nature of color changes that are interpreted by the operator.
Based on our own experiments and interviews with local law enforcement, the most common mistakes in using these tests include user error (most common is using too much sample), subjectivity of result interpretation, and lack of proper training. The training CD from Safariland that contains a PowerPoint presentation is useful for understanding how to use the test, but it lacked detailed instructions, actual photos/images of the NIK® tests after testing drugs, and had no clear depiction of the color development when there were multiple phases in the pouch. Also, some pouches in the kit had directions listed on the front, while others did not so the CD had to be consulted.
Unfortunately, while the NIK® test has impressive analytical power, the test is not accompanied with real photos of test results. The user has to rely on a color chart, which is subjective and not always representative of a real life color change. Therefore, we tested the kit, took photos and wrote detailed reports that can be used by anybody who uses the test, aiming to assist policemen or correctional officers when they are NIK® training and testing drugs on a crime scene.
Results and Discussion
On April 24, 2018, the Superior Court of California, County of Imperial, Case Number JCF 36904, dismissed the Grand Jury Indictment [Penalty Code Paragraph:995] and ordered the NIK® tests as inadmissible evidence to give it reasonable cause for indictment. The ruling was based on that fact that no validation studies can be found in the literature of the NIK® tests, especially with abused drugs. Furthermore, there is lack of evidence that NIK® tests are accepted by scientists and experts in the field as a valid drug tests due to the occurrence of false positives. Also, the NIK® test were carried by correctional officers who are not experts in the field of colorimetric testing, and they did not understand the meaning of a positive or negative results, especially since correctional officers use the IDENTIDRUGTM Chart or the color that is depicted on the test pouch.
Therefore, there is a need to present data and reports with actual photographs of the NIK® tests after testing with drug samples, cutting agents, and substances that may create false positives. This way correctional officer do not just rely on the subjective color interpretation of a color change in the pouch and comparing that with the color on the IDENTIDRUGTM Chart or the color that is depicted on the test pouch.
Table 1 shows the color observations of cocaine and cutting agents. Table 2 shows the description of incorrect results of sugar, cocaine, and cocaine mixed with sugar. Table 3 shows the controlled substances, and Table 4 lists cannabinoids and THC. All reports with detailed instructions, photographs, observations and notes, as well as conclusions are assembled in the supplemental information.
Table 1:Summary of NIK® tests with cocaine and cutting agents
Table 2:Description of incorrect results of Sugar, Cocaine, and Cocaine cut with Sugar.
Table 3:Table of Controlled Substances/Medications
Table 3:Table of Controlled Substances/Medications
Table 4:Table of Marijuana and Cannabinoids
This report attempts to provide users of the NIK® test with real detailed reports and real images so that a better presumptive interpretation can be made with regards to positive or negative test results, giving users a true comparison of the results in the field with an actual picture instead of a color chart that is provided with the NIK® test.
This publication was made possible by the US Army W911SR-15-C-0027 SBIR Phase I -Chemical Biological Radiological Nuclear and Explosives (CBRNE) Reconnaissance Sampling Kit (A15-048), and the National Science Foundation (Grant No. 1459838), and the Henry Dreyfus Teacher Scholar award for AH. We thank the Police Department in Crete, Nebraska, for their help in analyzing a real marijuana sample with the NIK test. We thank the Nebraska State Trooper Department for providing a perspective on the NIK test. We thank the Nebraska State Crime lab for their perspective about false positives with the NIK test. We thank Pat and Mary Williams of Sangre AgroTech for testing real marijuana samples with the NIK test.