The study is a psychobiographical study, aiming to explore and describe the life of John Wayne Gacy. He was a well-respected man in his community, entertaining the neighbourhood as Pogo the clown. But there was a dark side to his nature that he tried to keep hidden; yet glimpses of it appeared throughout his life. This dark side was exposed to the public when the police found twenty-seven dead bodies ranging from boys of nine to young men twenty years of age hidden in his basement. The study utilises the Erikson’s psychosocial developmental theory in order to examine Gacy’s life and attempt to establish unique character traits. The study utilises a qualitative single case study approach, and the subject was selected through purposive sampling based on interest value. Archival data was collected from secondary sources to enhance validity. Data was analysed by first organising and reducing information obtained; and then displaying it for discussion of Gacy’s life. Gacy’s life was reconstructed from birth, through adolescence and adulthood and his death. The findings suggest that the theoretical approach considered the biopsychosocial as well as cultural and historical influences of situations and experiences in Gacy’s personality development throughout his lifespan. The main themes of discussion centre around the abuse he experienced and the influence this had on his development, the lack of crisis resolution and thus achievement of virtues, Gacy’s lack of difficulty in establishing attachment and the resulting narcissism and lack of self-abandon, as well his homosexuality, sadism and the murders he ultimately committed. The study highlighted the importance of psychobiographical studies and the value of Erikson’s theory in understanding development. Recommendations for future research in this field was made in the hope of further uncovering and understanding the personality and its development.