The CSIs are puzzled when evidence and witnesses point to John McEnroe as their murder suspect despite his air-tight alibi, and as Mac's investigation causes a political firestorm, the team worries he'll be dismissed when they are asked to testify. Tennis Legend John McEnroe Guest Stars in a Dual Role. Mykelti Williamson ("Forrest Grump") guest stars as Chief of Detectives Brigham Sinclair, who leads the investigation against Mac Taylor.