The authors report the case of a 41-year-old man known as a polydrug addict and found dead at home. The initial toxicological screening was inconclusive for a toxic death. However, 7 small bags of unknown powders and crystals, supposed to be NPS, were found near the body and sent to the laboratory 3 weeks later. This article focuses on the interest of nuclear magnetic resonance (NMR) spectroscopy to solve this fatal case. The 7 items were identified by 1H NMR and their purities were measured by the quantitative NMR (qNMR) method using maleic acid as internal standard. The compounds were 4-chloro-α-pyrrolidinopentiophenone, dibutylone, 4-chloroethcathinone, 4-α-pyrrolidinohexuiphenone, 3,4-methylenedioxy-N-benzylcathinone, 3-methoxy-phencyclidine and α-pyrrolidinopropiophenone, with purities in the range 51–89%. In the biological specimens of the victim, only 3-methoxy-phencyclidine (3-MeO-PCP) was identified in cardiac blood, peripheral blood and urine at 743, 489 and 16,700 ng/mL. Hair (6 cm) concentration of the drug was 15,600 pg/mg. The other NPS were not detected. The peripheral blood concentration was higher than the values reported in previous intoxicated and fatal cases. The toxicological significance of the measured concentration in hair was difficult to establish because this is only the second case describing a test result for 3-MeO-PCP.