LSJ

αἴτιος αἰτέω

I. to blame, blameworthy, culpable, Il., etc.: comp., αἰτιώτερος more culpable, Thuc.; Sup., τοὺς αἰτιωτάτους the most guilty, Hdt.; τινος for a thing, id=Hdt.
2. as Subst., αἴτιος, ὁ, the accused, culprit, Lat. reus, Aesch., etc.; οἱ αἴτιοι τοῦ πατρός they who have sinned against my father, id=Aesch.:—c. gen. rei, οἱ αἴτ. τοῦ φόνου those guilty of murder, id=Aesch.
II. being the cause, responsible for, c. gen. rei, Hdt., etc.; c. inf., Soph.: Sup., αἰτιώτατος ναυμαχῆσαι mainly instrumental in causing the seafight, Thuc.
2. αἴτιον, τό, a cause, Plat., etc.