A federal judge certified a class of about 28,000 prisoners in a lawsuit accusing the Illinois Department of Corrections of violating the U.S. Constitution by overusing “extreme isolation.”In a written opinion, U.S. Magistrate Judge Mark A. Beatty of the Southern District of Illinois held the class proposed by the six named plaintiffs meets the requirements for certification set out in Federal Rule of Civil Procedure 23.The suit alleges the corrections department is putting too many inmates in extreme isolation …