It is not magic, but, as other posters alluded, sometimes it can be merely an educated guess. It is hard to accept a life changing verdict based on a guess.. even if it is an educated one.
So no, each time a given technique is used, the way it works has to be explained so that a decision based on facts of the case is made.
Nothing wrong with that, but a common sense explanation by an expert witness ought to be enough. Does Apple need to be dragged into each and every case to testify as to how pinch to zoom works, as was demanded here?
Courts have established mechanisms for handling technical questions around evidence. It's not like any of this is new.
The judge did not give the prosecution time to find an expert witness, did not ask his clerks to search for similar usage of iPad zooming in previous cases, and did not require the defence to provide expert testimony of their own to substantiate their claim.
In the end the iPad was not used. Instead a 4K TV was used, which ironically probably upscaled the image too.
This wasn’t a new evidence exhibit being introduced. Did you actually read the transcript, or are you reacting to this story based on what you’ve read elsewhere?
So no, each time a given technique is used, the way it works has to be explained so that a decision based on facts of the case is made.