As the other attorney stated, questionable tint is a valid reason to stop a vehicle. For a better idea of what constitutes reasonable suspicion, read Terry v. Ohio, 392 U.S. 1 (1968) and Arizona v. Johnson, 129 S.Ct. 781 (2009). They are both landmark cases and have wide reaching applicability. If you still have questions after reading these two cases, consult an attorney.
The above advice is intended to be educational only. Any legal issue(s) should be brought to the attention of a licensed and qualified attorney in your state of residence. No attorney-client relationship exists or should be construed to exist by virtue of this post.
You were cited for improper passing because the officer is alleging that you didn't use your signal and your actions interfered with the movement of his vehicle. The tint violation could have been discovered after the officer stopped you for improper lane change. If you disagree with the Officer's side of the story, take it to court, but only with an experienced traffic attorney by your side.
If you were cited under 316.085(2), the language of the statute reads: "(2) No vehicle shall be driven from a direct course in any lane on any highway until the driver has determined that the vehicle is not being approached or passed by any other vehicle in the lane or on the side to which the driver desires to move and that the move can be completely made with safety and without interfering with the safe operation of any vehicle approaching from the same direction."
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