DA question about "Items already in review"

Hello,

Just needed to confirm something, legal was asking me about "Include items already in review". They wanted confirmation that this setting is at the case level? So if the legal person runs a search and does not select "Include items already in review but another legal case has the email she is looking for already in review will it be captured in the new search? Hope that makes sense, I know generally it is a good idea to select this option but wanted to see how it worked between multiple cases or if the setting is only internally to that case?

Thanks,

Travis