Can a Party Demand Information From The Other Party?

Rav Dovid Josilowsky 

Question: 

I am in the middle of a din Torah and I feel that the other party is withholding information. May I demand that he produce the proofs and documentation that he has? 

Answer:

The Shulchan Aruch rules that if someone knows that the other party has a specific document that will help his case and the person admits that this is true, then he must show it to the Bais Din. 

If he isn’t citing a specific document but claims that there is evidence in general, it is up to bais din to assess whether or not there is merit to the claim. If there is, the litigant must produce this documentation and provide it to the bais din in order to be able to come to the truth of the matter.  

The Teshuvos Rivash explains that bais din’s goal is to get to the ultimate truth in order to issue a just ruling, and if demanding the evidence and documentation is necessary for this aim, they should do so.