There is no pushing of guilt. I simply do not understand how this can be a factor in the absence of overwhelming evidence against the defendant. You probably saw at least some of the OJ trial. Tons and tons of emotion, and yet the jury was bound by the rules of reason, the rules of the court, the rules of admissibility, etc, etc... and they returned a verdict that, to some, seemed absurd. They acquitted a guy that had already been sentenced and hanged by the court of public opinion. Many of the jurors themselves were pissed, but hey, they had to decide based on certain rules, and they did. So will this jury.
Without overwhelming evidence, all you've got is a guy sitting on one side of the room, and the mother weeping on the stand, and until both you and I have actually read this case, especially the content of her testimony, I refuse to believe that her role as a witness is worthless. If it was, the prosecution would have sustained an objection to present the witness in the first place.
If her crying does anything to the jury, it will only be to stiffen the sentence. And if the guy is guilty, then he should get the maximum punishment for a double murder anyway.
Without existing evidence, there is simply too must disjointment between her tears and the defendant. As already mentioned, the whole concept of 'oh, I really feel for the mother, the guy must be guilty', just doesn't work.