Usage patterns
〈事〉の因果を探るto investigate the cause and effect of something
The detective took action to investigate the causal chain behind the incident.
因果な〈事〉an ill-fated, unlucky ~
It's a cruel twist of fate, but he lost his parents right after he was born.
因果に苦しむto suffer because of one's karma/fate
She believes she is suffering because of karma from a past life.
Expressions
惚れたが因果love is an unfortunate fate; you can't help falling in love, no matter the consequences