Criminal
Culprit
noun
A crime person is a criminal.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
クッキー食べた犯人、お父さんだった。
The culprit who ate the cookies turned out to be Dad.
まだ犯人つかまってないらしいよ。
I heard they haven't caught the culprit yet.
その犯人は、口は災いの元だということを思い知った。
The criminal realized that the things he said truly were evil.