Doxylamine, which is an active drug ingredient used for insomnia, is an antihistaminic with sedative effect and can be received without a prescription. Although doxylamine succinate intoxication is encountered quite frequently, there is no data that shows the drug is used for intentional injury. This study was conducted to unravel a suspected case of intentional poisoning facilitated with the use of doxylamine, using a fast, accurate and reliable chromatographic method. The complainant realized that she had fallen asleep after drinking the tea given to her by her colleague, who has been treating her badly for some time. After experiencing a second similar situation, she asked for toxicological analysis. The analysis revealed the presence of 69.3 mu g/mL (13.9 mg/cup) of doxylamine in the sample, and it was concluded that this amount was sufficient to produce the symptoms the complainant mentioned. However, this study reveals that the complainant's claim is quite difficult to prove, and toxicological analysis alone are not enough to prove her claim. Considering the possibility of crimes of intentional injury, aspersion and torment on a legal basis, this study thought to be remarkable as it presents a case of suspected crime facilitated with the use of an active drug ingredient.