In military courts of law, the "good soldier" defense is often used by the defendant to explain the presence of THCA above the DOD established limit of 15 ng/mL. The defense will contend the defendant unwittingly breathed side-stream marijuana smoke, thus resulting in the presence of THCA in the defendant's urine. The purpose of the current work was to link an indoor air quality model (IAQ) with a pharmacokinetic (PK) model to predict a passive marijuana smoker's resultant concentration of the major urinary metabolite THCA. A three-compartment design was used for the residence; it consisted of the source room (30 cubic meters), the rest of the house (250 cubic meters), and the outdoors. The air-exchange rate between the source room and the rest of the house was 1.0 air-changes per hour (ACH), and between the rest of the house and outdoors, 0.5 ACH. These values are typical of a small residence. The source term was 0.24 mg/hour of THC released to the air by the person smoking the marijuana. This is equivalent to six 2.5-percent NIDA-certified marijuana cigarettes smoked over the course of 1 hour. The pharmacokinetic (PK) model was built using real-world measurements taken from the literature for a standard 70-kg male. The PK model treats the body as a single compartment in which absorption occurs through inhalation of side-stream marijuana smoke. Initial results from the model's application show that at the end of the 8-hour exposure period, the passive smoker in the source room attained a level of 4.4 ng/mL, significantly less than the 15 ng/mL set by the DOD. The passive smoker in the rest of the house measured 2.6 ng/mL in the urine. These values are comparable to experimental results reported by others. 1 table, 3 figures, and 7 references