Someone asked me about "unwitting sins." My reply:
i) Not all sins are crimes. The Mosaic law tends of focus on sins that are socially disruptive. It has a communal emphasis.
Conversely, not all crimes are sins. Some crimes are technicalities. Laws of utility rather than morality.
ii) In Leviticus, the focus is generally on ritual purity and impurity. That's fairly artificial. More about symbolic holiness or unholiness than actual holiness or unholiness.
In that respect, the offender may not have done anything intrinsically evil, so long as it was committed through ignorance or inattentiveness.
iii) Ps 19:12-13 is ambiguous. Ross thinks it refers back to the Pentateuchal distinction between unwitting sins and the highhanded sin. But Goldingay thinks it refers to conspiracies, secret plots, covert unauthorized worship–which subverts true worship–by "willful" agents. Hard to choose between these competing in interpretations, since the wording isn't that specific.
iv) The key interpretive text is Num 15:27-30. Unwitting sin is defined, not in isolation, or on its own terms, but in contrast to highhanded sin.
The highhanded sin is less about personal ethics–although that's included–than social ethics. It has a communal dimension. An act of open rebellion.
If allowed to go unchecked, that has a demoralizing effect on the religious community. The more people get away with it, the social fabric begins to unravel. Unless it's nipped in the bud, impudent disobedience becomes an incitement to national apostasy.
People can sin with impunity. There is no fear of God. God's law is held in contempt. The people revert to heathenism.
There is no sacrifice for this sin because the defiant attitude is intentionally impenitent.
The wording of the punishment is ambiguous. Harrison thinks it alludes to capital punishment, but Currid thinks it alludes to banishment.
I incline to Currid's interpretation. If so, the nature of the punishment illuminates the nature of the offense.
It is not, strictly speaking, an unforgivable or damnable offense–although that may often be the case–but an excommunicable offense. And that's because the rebellious behavior is detrimental to communal norms. Implicitly seditious.