From my cursory reading of the topic, three is basically no precedent for jailing such ransom-paying parent, and securing a conviction with a jury is very unlikely
Yes, I should probably clarify: the point of such a law is to _discourage_ the behavior, but not to actually _punish_ the ransom payer, since no jury is going to vote on putting grieving parents in jail. So you end up deterring ransom payments without actually introducing negative externalities.