Sounds a bit blatent, filming openly like that, and it would spook me.
But surely if they were after evidence, you'd covertly filmed, with a miniature camera in a button or something?
When I drive to and from a punt, I watch my mirrors carefully, and if I have the slightest suspiscion, I go on a detour to see if I am followed before going home to lose them, as I live in short cul-de-sac, so it's a give away other wise.