A great deal of energy is being spent by the government, the justice system, and various commentators on the guilt or innocence of David Bain. (He spent many years in prison for murders, but has since been acquitted.) An example is the opinion piece in the Herald by C K Stead (Opinion: Why judge was wrong on Bain - Politics - NZ Herald News).
Some people continue to think David Bain is guilty, but it is evident that at least one jury, and a number of highly qualified legal practitioners, think there is not enough evidence to prove his guilt (and a substantial number of people believe him to be completely innocent).
The level of interest in his guilt or innocence reflects a deep-seated unhappiness at the thought that a guilty person might go free. This unhappiness is, I believe, a God-given sense that something is broken in the world if evil deeds are not dealt with.
Similarly, Joe Karam's campaign to free David Blain reflects a God-given horror at the thought of punishing an innocent person for someone else's crimes.
But the Christian can regard this case with peace of mind. Christians are more concerned with the freedom of innocents than the punishment of the guilty. An innocent person's unjust imprisonment has an effect that cannot be reversed—this life is ruined for them (although they might potentially enjoy freedom in the next). But a guilty person's crimes never go unpunished.
If someone commits a crime, but there is too little evidence to convict them in a court of law, we simply remember that eventually they will have to answer to God for their actions (as we will ourselves). That is a court in which the guilty never escape on a technicality.
As a result, Christians are right to make sure that justice is biased towards freeing the innocent, even if that results in some guilty people going unpunished in this life. The burden of proof for crimes in our legal system (beyond reasonable doubt) reflects a Christian understanding of the world, and a Christian belief that judgement always meets evildoers—in this life, or the next.
The angst in the public debate results from society's loss of belief in God's day of reckoning.