I don't practice in MD, but in most jurisdictions you do. However, you may not need to if there aren't any cars behind you. I'd look up the statute or code section you got ticketed for.
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I don't see anything in the rules that would indicate that you are required to use a turn signal in the situation you described. If you received a ticket, your ticket should cite the traffic law that you violated. Laws have elements that have to be proven in order for you to be found guilty. If the elements are not met, then you can be found not guilty. A traffic attorney can provide assistance in reviewing the rule, the facts of your case and advising you of any defenses you may have.
Answers to questions are not legal advice but information for general use only and do not form an attorney-client relationship.
If your ticket doesn't cite a specific statute, then you might have grounds to challenge it. Contact a local attorney for more guidance.
DISCLAIMER: Brandy A. Peeples is licensed to practice law in the State of Maryland. This answer is being provided for informational purposes only and the laws of your jurisdiction may differ. This answer based on general legal principles and is not intended for the purpose of providing specific legal advice or opinions. Under no circumstances does this answer constitute the establishment of an attorney-client relationship. For legal advice relating to your specific situation, I strongly urge you to consult with an attorney in your area. NO COMMUNICATIONS WITH ME ARE TO BE CONSTRUED AS ARISING FROM AN ATTORNEY-CLIENT RELATIONSHIP AND NO ATTORNEY-CLIENT RELATIONSHIP WILL BE ESTABLISHED WITH ME UNLESS I HAVE EXPRESSLY AGREED TO UNDERTAKE YOUR REPRESENTATION, WHICH INCLUDES THE EXECUTION OF A WRITTEN AGREEMENT OF RETAINER.