Simple:
* The detective finally caught the culprit responsible for the robbery.
* The culprit was found hiding in the attic.
* The culprit was a disgruntled employee.
More complex:
* After weeks of investigation, the authorities finally identified the culprit behind the cyberattacks.
* The culprit, a disgruntled employee, had planted a virus in the company's system.
* The culprit, although caught, was never brought to justice for their crimes.
* The culprit in the car accident was found to be driving under the influence of alcohol.
Figurative:
* Stress is often the culprit behind many health problems.
* Lack of communication is the culprit in many failed relationships.
* The culprit in the team's poor performance was a lack of leadership.
Remember that "culprit" generally implies someone who has committed a crime or a wrong, but can be used in other contexts to refer to the cause of a problem.