Since this word is made up of a single kanji, it should use the kun'yomi reading. When learning the kanji, you didn't learn that reading, so here's a mnemonic to help you with this word: When you come to confess your sin to me, you start claiming it wasn't you. You say it was some other version of you! What? How could this be? Well, you say "there are two mes (つみ) out there!" One is doing the bad stuff, and the other is you, and you haven't done any sins!
Mami's crime of eating Koichi's bacon is more serious than she thinks.
My company president has been found guilty of accounting fraud crimes.
I don’t think Koichi would hire anyone who has committed the crime of murdering innocent civilians.