Most aren't qualified to make a legal determination, as aren't most cops.
IF you get the cop on the stand and ask him what facts he relied upon to determine that he had jurisdiction and that a crime had occurred, the da will be quick to not allow him to do that on the stand, he isn't qualified.
The da allowing him to testify to something he isn't qualified to testify about is a crime.
Then you move to strike the witness' testimony and for the dismissal of the case for lack of presenting a case.
Marc Stevens was silenced too soon, imo.