You've got first-degree murder, conspiracy to commit murder, shooting into an occupied vehicle, and using an instrument to harm a fetus. That way, if a juror is adamant in saying they will not ever vote for first-degree murder because he didn't pull the trigger, that juror perhaps can be talked into voting for conspiracy to commit murder. Well, sometimes logic goes out the window. It's a compromise. If a jury's been in there two or three or four days or however long, there will be factions within the juries, and at some point in time if they get in a deadlock, the judge will instruct them to make a decision.
Juries go about their deliberations in different ways.
Sometimes, once they pick a foreman, they take an initial straw vote before really discussing the evidence to get a general gauge of where each juror is. Other jurors sift through the evidence and discuss it in great detail before taking an initial vote. I expect this jury will be meticulous in reviewing the evidence, and I would very surprised at a quick verdict either way. If the jury cannot reach a verdict, then the case has to be tried all over again, or the prosecution has to dismiss the charges, or the defense has to agree to a plea. It's unlikely either side will agree to that kind of compromise.