Yes, you do have a better argument to get it dismissed if the officer does not show up if you have not waived time (i.e., if you accept the May 7 date). If the court attempts to reschedule, you can and should argue that rescheduling (beyond 45 days from when you requested TDN) violates your constitutional speedy trial rights. If you have waived time,. you can still argue that rescheduling would be unfair to you for whatever reasons you can think of (having to skip work or school, travel far from your residence, etc.)

