It is a piece of evidence. The jury would decide how much weight to put on that evidence. Depending on other factors, the jury could decide it is compelling and provides reasonable doubt, or, they could decide it is not compelling and disregard it and look at all the other evidence regardless of this particular bit.

Edit to add: Prior to trial there is a jury of one, the prosecutor. There is a chance that the prosecutor will find that evidence compelling and not even bring charges, or dismiss them if they were already brought.

Tell them the vaccine for not being whalloped with your baseball bat is to shut up about that stupid anti-vaxxer shit and you highly recommend they take that vaccine.