Peter Leithart draws helpful distintions between sin and guilt, the act of transgression and the responsibility that follows it:

I have in mind the phrases “he shall bear his iniquity” (Leviticus 7:18; 19:8) and “their/his blood on them/him” (Leviticus 20:9).  In Leviticus 20, the phrase occurs in a context prescribing capital punishment.  When the text adds “his blood is on him,” the implication is that the blood is not on the people who shed the blood – namely, the citizens who stoned the criminal.  But a further implication is that the blood must be on someone. Free-floating blood, as it were, is not an option.  Either the person who committed the crime must bear responsibility, or the people who failed to carry out the punishment, or, in some cases, a substitutionary animal must bear responsibility for the crime.  That is, some assignment of responsibility is necessary.

That seems to presume that there is some distinction between the act itself and the assignment of responsibility for the act.  When a man takes his sister as a wife, he is “cut off in the sight of the sons” of Israel (Leviticus 20:17).  That probably does not refer to a death penalty but rather to something like excommunication.  Whether or not that is correct, the statement is followed by the declaration that he “bears his guilt.” But if the wrong action attracted guilt to it “immediately,” then the additional statement that he bears his guilt is redundant. Of course he bears his guilt; who else would?  But the fact that the phrase is included at all suggests that someone else might, and thus suggests that the assignment of responsibility or guilt is a distinct “event” from the wrong action itself.   In short, wrong acts must be judged wrong.

There’s a particular spin on this for capital crimes.  A man, for instance, has homosexual relations in ancient Israel, and by the Torah must die (Leviticus 20:13).  He has committed a wrong, and must be punished.  But his death leaves the land bloodstained, and that can’t be left alone.  Somebody has to pay for that additional bloodshed.  The law says that the person who died paid for it with his death.  His execution is a punishment for the crime, and the bloodshed involved in his death is assigned as his responsibility.  In a sense, there’s a kind of double jeopardy here – the man dies once for two different wrongs – the wrong of his original sodomy and the wrong of shedding blood on the land.  The Torah treats his bloodshed as if it were suicide – “his blood is on him.”

If there’s always an assignment of responsibility distinct from the wrong of the act itself, then that leaves open the possibility that someone other than the actor might bear that responsibility.  It suggests the possibility that the iniquity might be “imputed” to another, to a sin-bearer.  On this theory, “imputation” is not what happens when someone else takes the guilt; imputation is necessary for any assignment of guilt, whether to the perpetrator or to someone else. Every sin and crime must be imputed in order to be punished, by the sinner or criminal or by the substitute.

This makes sense of the sinner’s status as still a sinner and yet also a forgiven and thereby righteous saint. Read the whole thing here.