To charge someone for withholding evidence, wouldn't you have to show that they had the evidence? For example, in the case of a deleted file, you would have to

To charge someone for withholding evidence, wouldn't you have to show that they had the evidence? For example, in the case of a deleted file, you would have to show that they deleted the file after being charged. Else deleting any file ever would potentially be a crime. Now consider the case there that file is the encryption key.