olemus
Wiktionary:
4. (law, uncountable) a pre-trial phase in which evidence is gathered
The prosecution moved to suppress certain items turned up during discovery.

discovery of documents -- dokumentide väljanõudmine
discovery of evidence -- tõendite kindlakstegemine

ülevaateid
https://www.hg.org/legal-articles/what-is-discovery-in-a-civil-case-30930

https://www.allbusiness.com/how-to-conduct-discovery-for-your-court-case-4136-1.html