I'm not sure you understood my question. Grand larceny is a felony, which means he has a Constitutional right to a trial by jury. Of course, there would be a judge presiding, but it's the jury who would determine guilt or innocence. Sometimes a felony defendant will agree to waive a jury and have the case tried directly to the judge. So I was actually asking if he was going to have a jury trial.
If so, it is very unlikely that the trial will end on the same day the trial starts. It could take a whole day to empanel and choose prospective jurors. And then there would be opening statements, all the state's witnesses would have to testify and be cross examined, and then the defense may or may not put on witnesses too. Then there are closing arguments, followed by the judge's charge to the jury before they deliberate. How long the jury would take to reach a verdict is nothing one can guess at. Figure a jury trial for something like this, start to finish could run 4 or 5 days.
With a trial directly to the judge, a lot of the formality gets dispensed with because the judge is already familiar with the evidence. It is possible that the trial could be held and the verdict rendered in one day, depending upon how many witnesses have to be heard from, but it might take another day or two all the same because judges don't clear their entire calendar for a bench trial. They tend to see other cases during the day as well, unlike with a jury trial.
A final possibility is that there will be no trial at all, and on the day of trial your son in law will agree to a plea bargain. That's fairly common, particularly when the defendant knows he has a weak case but has been hoping all along that the complainant won't really press charges.