Is non-consented video recording admissable evidence in a civil trial
I am assuming t hat the person who took the video was not a law enforcement officer and was not acting in concert with a law enforcement agency. This assumption isn't strictly necessary to resolve the question, but it makes the analysis simpler and seems to be implied in the question.
The U.S. Constitution does not require the exclusion of evidence obtained illegally by a private person independently of law enforcement, and does not require the exclusion of evidence obtained illegally in a civil lawsuit.
There is also no federal law which prohibits videotaping someone with their knowledge but not their consent.
So, the resolution of the question is purely a question of Maryland state law.
The Maryland Wiretap Act prohibits the use of material obtained in violation of the act in any court proceeding.
So, it is necessary to determine if the video recording was in violation of the Maryland Wiretap Act to determine if it is admissible.
The Maryland Wiretap Act makes it illegal in some circumstances to intercept an electronic communication and also makes it illegal to having a law enforcement officer use a hidden recording device to record a conversation in some circumstances. Taking a video of someone who knows that they are being videotaped, is not a violation of either of these provision of the Maryland Wiretap Act, without regard to consent.
So, illegality is not a bar to the admissibility of the evidence, unless some other Maryland law not mentioned in the question prohibits taking video of someone openly, but without their consent (which seems unlikely). If it wasn't illegal to take the video, then it can't be excluded from evidence on the grounds of illegality.
Therefore, if the plaintiff can show that the video is authentic and that the material in the video is relevant to the disputed issues of fact that are at issue in the case, the evidence should be admissible.