The general 'tradition' among soap writers confronted with this situation (which is, unfortunately, quite often) is to have the character punished in an alternate fashion, something that gives the viewer the feeling that the character is paying for his/her crime, but not in a direct way (prison). This is when they have to keep the character on the canvas because the actor is not going to be written out, no matter what he/she has done onscreen. Seeing Blake suffer in some alternate fashion (like losing something very important to him, or becoming disabled in some way) gives the viewer the feeling that justice was done, while also keeping the character around. It also (when done right) can serve as a challenge for the actor, who may want to re-direct the character from his/her illegal activities. If a character is allowed to skate too many times, viewers will turn against the character and the writers will be forced to write them out for good. If Blake manages to shake the charges, I'm pretty sure they won't try to let him get away with something this serious ever again.
In this situation, it's much harder to justify Blake being allowed to get off scot-free, since we basically saw the crime committed. The prison scenario in the first few episodes (with the scheme to get released on house arrest) didn't really appeal to me because NuDynasty isn't in the business of "gritty realism" (the best they could manage were prison yard scenes filmed in sepia tone with acting that seemed more like outtakes from West Side Story). While the scheming and lying to get Blake out on house arrest was clever and kind of entertaining, they would be stupid to write similar tricks for the actual trial, since the trial is supposed to be a serious reckoning. The best I could imagine--something lawyers often use--would be leaning HARD on "reasonable doubt" during the trial. Blake's attorneys could work with Anders to make it look like he actually killed Mack. Anders could actually play along, since he's not on trial and all they need to do is have the jury unsure of whether Blake did it. Of course all the build-up toward reasonable doubt could blow up in their faces when/if Alexis returns and says...well, whatever she wants to say. She could be Blake's savior or Blake's executioner depending on what kind of mood she's in.