Introduction: Diagnosing ventilator associated pneumonia (VAP) is difficult and is usually based on the criteria with high sensitivity and low specificity1 such as fever, leukocytosis, and infiltrative abnormalities on chest radiographs. In live patients the microbiological analysis of bronchoscopy samples are considered the most specific for diagnosis but not widely used. The Clinical Pulmonary Infection Score (CPIS), a diagnostic algorithm relies on easily available clinical, radiographic, and microbiological criteria. But all these will become hard in cases of medico–legal issue. A study was undertaken to assess the diagnostic value and the impact of microbiological investigations on the accuracy of clinical diagnosis of VAP. This helps to know the microbiological status of lung at the time of death. Method: A prospective study conducted by qualitative post–mortem culture of pulmonary aspirate taken from each lobe of both lungs among 50 medico–legal cases that were mechanically ventilated. Results: A sensitivity of 71% and a specificity of 70 was found among the cases where there was inflammatory infiltrations on the chest radiograph and two of three clinical criteria (fever, purulent secretions, leucocytosis). The post–mortem microbiological evaluation corrected the false positives and false negatives. Conclusion: Conventional clinical criteria have reasonable diagnostic values however Forensic–Microbiology investigations increase the accuracy in diagnosing a medico–legal case of VAP. This can also become a tool for uplifting the justice in such cases. The risk of under treatment and region–wise algorithm guiding antibiotic treatment exclusively by Forensic–Microbiology results improves both the clinical and judicial outcomes.