The phrase "turn somebody in" means-

• The phrase "turn somebody in" means- ক) To hand a person over to the police

• Turn somebody in
- English Meaning: to hand a person over to the police or authorities.
- Bangla Meaning: পুলিশ বা কর্তৃপক্ষের হাতে সোপর্দ করা।

• Ex. Sentences:
- She threatened to turn him in to the police.
- The hit-and-run driver turned himself in to the police the day after the accident.

Source:
1. Oxford Dictionary.
2. Website Lecture.