culprit
n. countablen. the person who is responsible for a mistake, problem, or crime. You use this word to point out who caused something bad to happen.
n. the person or thing responsible for a fault, crime, or problem. Often used metaphorically to identify the cause of a non-criminal issue.
The broken window was the culprit for the draft.
Police identified the suspect as the main culprit in the bank robbery.
After months of investigation, the committee finally identified poor communication as the primary culprit behind the project's failure.
From Anglo-Norman cul. prit, contraction of culpable: prest (d'averrer nostre bille) 'guilty: ready (to prove our case)', words used by prosecutor in opening a trial, mistaken in English for an address to the defendant. See culpable. It may have been influenced by Latin culpa (“blame, fault”).