how can the judge force the attorneys to put the right witnesses on the stand
Part - no, a LOT - of the problem is the utter incompetence of the Schindlers' attorneys.
This is another issue I have with the process - if you can afford a much better lawyer than the other party, you can buy the verdict you want. Financed by $400k+ from Terri's care fund, Michael bought an order of starvation.