The word "sin" is used loosely in everyday speech, but its only appropriate meaning becomes clear when sins are distinguished from crimes. In that clear usage, a sin is an act of disobedience to God, a violation of the Ten Commandments or of Christ's two precepts of charity.
One and the same act maybe a violation of both divine law and human law, but it is a sin only if it is an act of disobedience to God's commandments or precepts. It is a crime only with regard to human positive law. We cannot sin against our human neighbors when we treat them unjustly.
In the Lord's Prayer, we ask to be forgiven for our trespasses as we forgive those who trespass against us. We cannot ask to be forgiven by God for sinning against other human beings.
You may ask about violations of the natural, as distinct from the positive law. Such violations are immoral and unjust acts, and they may be both sins against God and crimes punishable by the state. (See Law.)
Adler's Philosophical Dictionary (1995)
Great Ideas from the Great Books (1963)
by Mortimer J. Adler