You can use WorkParties to keep track who has already been a reviewer for a case. It is possible to generate a NOT IN clause using a "Do Not Join Rows" Report Definition subreport or you can finagle a ListView to generate the equivalent by using NotEquals against a ValueList or CSV List.

The query below would be used when multiple Review cases are created to review the same parent case. Each Review case is parked a workbasket. The WB does not need to be same WB for each Review case.

Note how the Review cases in the query below share the same pxCoverInsKey. In your situation remove the word "Cover" .

select pzInsKey from {Assign-WorkBasket} WB, Org-App-Work-Review} REV
where WB.pxAssignedOperatorID = [workbasket]
  and WB.pxRefObjectKey       = REV.pzInsKey
  and REV.pxCoverInsKey not in
        (select REV2.pxCoverInsKey from {Org-App-Work-ReviewCover} REV2, {Index-WorkPartyUri} WP
         where WP.pxInsIndexedKey   = REV2.pzInsKey
           and WP.pxPartyRole       = "Reviewer"
           and WP.pyPartyIdentifier = OperatorID.pyUserIdentifier)