Мотив преступления [motiv prestupleniya] literally means “motive for a crime.” It is a striking phrase because the singer uses crime imagery metaphorically, calling the person she loves her irresistible reason to break the rules, while insisting she does not regret it.
This is a song about a love that feels a little like breaking the law, and Lyusya Chebotina is having way too much fun to feel guilty about it.
The hook says it all: "Ты мой мотив преступления" (You are my motive for a crime), followed by "Но я ни капли не каюсь" (But I don't repent one bit). Ни капли literally means "not a drop", a very Russian way of saying "not at all". Then she shrugs off everyone else with "Плевать на все осуждения" (I don't care about all the judgment). Плевать literally means "to spit", and плевать на is the everyday way to say you couldn't care less. My favourite line is the strange, teasing request "Целуй меня не касаясь" (Kiss me without touching).
The verses are full of great idioms. "Совесть нервно курит в сторонке" (My conscience is nervously smoking off to the side) is a joke Russians use when something is so outrageous that even your conscience has stepped away and given up. She jumps onto a departing train "будто скорость подчиняется мне" (as if speed obeys me), asks for a тет-а-тет (a private meeting, borrowed from French tête-à-tête), and adds the cheeky "Мне пока не 30 лет" (I'm not 30 yet), as in: there's still time to be reckless.
The second verse keeps the crime theme going. "Не доступен абонент" (The subscriber is unavailable) is the recorded message you hear when a Russian phone is switched off, here meaning she is unreachable for anyone but him. And "Без улик и дела нет" (No evidence, no case) is pure detective-show language: if nobody can prove it, it never happened. It's playful, a bit dramatic, and very catchy.