Introduction: Cyanide toxicity has been well known for over two centuries and, although most cyanide intoxication cases are accidental, such as fire victims, cyanide poisoning is sometimes motivated by suicidal or homicidal purposes. Methods and findings: The method proposed in this study uses Headspace extraction and Gas Chromatography coupled with a Nitrogen and Phosphorous Detector (HS-GC/NPD), which has presented good results for both detection and quantification of cyanide intoxication, with satisfactory sensitivity and reproducibility. Good linearity (r2>0.99), accuracy and precision were achieved. Limits of detection and quantification were well below the lethal cyanide blood concentration. Conclusions: The present method is suitable for detection of cyanide intoxication even at small concentrations, and has been successfully applied in two lethal cases of cyanide intoxication.