The psychology term that describes the tendency of a person to blame others for their own faults or mistakes is "projection." Projection is a defense mechanism where individuals unconsciously attribute their undesirable feelings, thoughts, or traits onto someone else. By doing so, they avoid facing or acknowledging those feelings or traits within themselves.
For example, if someone is feeling guilty about their actions but doesn't want to accept that guilt, they may project their feelings onto another person and accuse them of the same actions they themselves have committed.
Projection can be a way for individuals to protect their self-image and maintain a sense of superiority or innocence. It's a common phenomenon in human behavior and is studied in various branches of psychology, including psychoanalysis and personality psychology.