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Criminally, it is a misdemeanor to use a hidden camera in a bathroom, dressing room or any area where it would be reasonable to believe the person would not be visible to the public. Md. Crim. Law §§ 3-901, -02. This means that if he is sticking the camera into a hole in the fence, or, is taping over a wall that is meant to block someone from seeing by using some kind of a ladder, etc, then this may be seen as a criminal offence. Violators of the hidden camera law can face misdemeanor charges with penalties that include up to one year in jail and a $2,500 fine. Md. Crim. Law §§ 3-901, -902, -903.
Civilly, he can be sued for invasion of privacy - intrusion on solitude. This means intruding upon another's solitude or private affairs, physically or otherwise, is subject to liability if this intrusion would be considered highly offensive to a reasonable person. Aside from punitive damages and legal fees, an injunction can be ordered by the Court against him.
But this all depends on the method and the situation. If there is no wall or fence, and he is simply pointing a video toward the yard of your home, this would likely not be actionable. However if he is going out of his way to overcome a wall/fence to tape, thus intruding on what someone in your situation would otherwise reasonable expect to be a private area - this is actionable.
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