Eyewitness testimony is often not entirely reliable, but it is still a category of evidence that should be considered. Video can’t show you what people were thinking at the time or describe what could be seen from other vantage points. There are plenty of things to be concerned about when a death occurs during training—was there a conspiracy to harm this person? A conspiracy to cover up an accident?—and one way to gather evidence on that is to get testimony from witnesses without giving them the chance to talk to other witnesses or to view other evidence. Mismatched statements can be significant, as can be surprisingly uniform statements that run counter to what the video shows. No one is suggesting their testimony is infallible, but neither is video evidence (because again it can only provide evidence from a specific vantage point). We want their testimony, though, without them having the chance to revise it or even just change their memory (memory being as fallible as it is) as a result of having seen the video.