Pneumothorax is a common cause of preventable mortality in combat environments, where needle decompression is frequently performed by personnel with limited training and variable success rates due to inconsistent landmarking and chest wall thickness variability. The Automated Needle Decompression Device (ANeeD) was designed to enable ultrasound-guided automated decompression. This study evaluated the device’s mechanical and algorithmic performance in six human cadavers with 53 total deployments across standard anatomical sites. The device successfully penetrated skin and subcutaneous tissue in all attempts and achieved full three-layer penetration—including parietal pleura—in 50 of 53 deployments; failures were due to rib strikes. Needle depth accuracy was within 3 mm in 98% of successful deployments. Ultrasound-based detection of rib margins and the pleural line reached within 3 mm accuracy in 66–76% of trials. These findings demonstrate that ANeeD can reliably penetrate human tissue to appropriate depths for pneumothorax decompression, although ultrasound algorithms require refinement. Future work should include improved sensor-needle alignment, enhanced image processing, and evaluation under dynamic or trauma-altered anatomical conditions.