Yes, recordings from a training exercise can be admissible as evidence in a court-martial to corroborate a conduct-based charge, provided they are properly authenticated and are relevant to the case. For example, if a service member is charged with dereliction of duty for failing to follow a specific procedure during a training exercise, a video recording of the exercise showing them performing the task incorrectly would be powerful corroborating evidence.
For the recording to be admissible, the prosecutor must first authenticate it under the Military Rules of Evidence. This means they must present evidence to show that the recording is a true and accurate depiction of the events. This is typically done through the testimony of a witness who was present during the recording, such as the person who operated the camera or another participant in the exercise. This witness would testify that they have reviewed the recording and that it fairly and accurately portrays what happened.
A military defense attorney can challenge the admissibility of the recording. They might argue that the video is incomplete, that it has been edited, or that it does not show the full context of the events. They can also argue that the recording is irrelevant or that its prejudicial effect outweighs its probative value. However, if the government can properly authenticate the recording and show its relevance to the charged offense, a military judge will almost certainly admit it as evidence for the panel to consider.