If there was solid external evidence of when a shooting occurred (eg gps timestamped video of the event) I could see them doing it purely for calibration purpos

If there was solid external evidence of when a shooting occurred (eg gps timestamped video of the event) I could see them doing it purely for calibration purposes. Clearly those adjustments should not be admitted as evidence in a court case. ShotSpotter just needs to take the 'L' and they will have to prosecute without (or admit whatever was originally recorded as corroborating evidence).