The sudden death of a female inmate shortly after her sentencing raised initial suspicions of cardiac arrest. However, forensic autopsy revealed key signs of poisoning. External examination showed macroglossia with dark discoloration, suggestive of severe upper airway edema. Internal findings included a white frothy substance in the trachea, congested and edematous lungs, and gastric contents comprising a blackish foul-smelling liquid, black shiny fragments resembling anthracite, and a knotted 10cm wool thread. The gastric mucosa appeared black and necrotic. Toxicological analysis confirmed the presence of paraphenylenediamine (PPD) in both blood and gastric contents. PPD is a highly toxic compound commonly used in hair dyes and known to cause multi-organ failure when ingested. This case underlines the importance of comprehensive forensic investigations in identifying concealed toxic exposures in custodial settings.