Since you mention it, you might be safer off just filming it. Dashcams arent legal in my jurisdiction either due to privacy concerns but people still use them.

What sounds like a crazy exaggerated joke(ok it is), there were actually cases where this happened and prevented people from being sentenced as rapists. The Gina-Lisa Lohfink case in Germany for example. The sex tape is arguably what saved these men from jail. An especially disconcerning part however is that the allegations were made after the video surfaced. So even with video proof it was a matter for a court with experts being called in to interpret the video.