The Clean Screen® THC solid phase extraction (SPE) column is UCT’s flagship THC sorbent. It has been on the market for over thirty years. Many forensic toxicologists undertaking medico-judicial investigations into THC and its metabolites turn to this sorbent to produce clean extracts and optimal recoveries. In a paper authored by Declues et al., (Journal of Forensic Sciences (doi: 10.1111/1556-4029.13168)) the Clean Screen THC columns were employed to analyze 1204 whole-blood samples confirmed to contain THC alone or in combination with other drugs out of nearly 5000 Orange County, California drivers suspected of driving under the influence of drugs in a extended time period. The goal of this study was to examine police reports and drug recognition expert evaluations of THC-positive samples within a 2-year time frame to determine whether there is a correlation between whole-blood THC concentrations and field sobriety tests performance. In this paper, cannabinoid-positive samples taken from drugs and diving suspects were quantified by use of the Clean Screen® THC SPE and a gas chromatograph/mass spectrometer (GCMS) selected ion monitoring (SIM) method to detect delta-9-tetrahydrocannabinol (THC) and its inactive metabolite, 11-carboxy-tetrahydrocannabinol (carboxy-THC). The limit of quantification (LOQ) for both THC and carboxy-THC was determined to be 2 ng/ mL in whole blood. This study using genuine drugs and driving cases demonstrates why forensic toxicologist turn time and time again to UCT’s finest sorbents for their analyses.