''Transactional Test'' to Decide Whether Separate Claims Considered the Same Cause of Action
In River Park, Inc. v. City of Highland Park, 184 Ill. 2d 290, 703 N.E.2d 883, 234 Ill. Dec. 783 (1998), in determining whether claims are part of the same transaction for res judicata purposes, the supreme court adopted the more liberal "transactional test" and rejected the "same evidence test," holding that the latter test is not determinative of identity of cause of action. River Park, 184 Ill. 2d at 310-11.
Rather, the court held, under the transactional analysis, separate claims will be considered the same cause of action for res judicata purposes if they arise from a single group of operative facts, regardless of whether different theories of relief are asserted. River Park, 184 Ill. 2d at 311.
The transactional test allows claims to be considered part of the same cause of action "even if there is not a substantial overlap of evidence, so long as they arise from the same transaction." River Park, 184 Ill. 2d at 311.