The problem is, we have to balance:
- societal justice (the desire that, overall, the system feels fair and people trying to 'cheat' don't ultimately profit (this is a goal, not a reality))
- public safety (removing harmful people from society to prevent them from causing more harm) [editted in]
- dissuasion (having steep enough punishments for future potential perpetrators to say the risk isn't worth it)
- reformation (the desire for the perpetrator to genuinely change his ways)
- vengeance (the desire for the victims (including family) to feel like the perpetrator has experienced some of the victims' pain. Call it a desire for enforced empathy)
- restitution (trying to compensate the victims for the wrongs done them)
[blue for victims' benefit, brown for perpetrator's benefit, cyan for society's benefit]
Add to that, as human beings - out of sometimes righteous anger, mostly unrighteous anger, pride, and/or self-righteousness - we tend to have a desire to crush and destroy and punish others for their crimes to make us feel better about who we are.
Sure, I'm not perfect, and I've said some things in the heat of the moment I've regretted, but that movie star made a racist remark - drag them into the streets and kneecap them!
But I do like the TV show they starred in, and their pretend apology two days later was sufficiently faux-humble that we'll "show compassion" and "forgive" them. Besides, someone else is here for me to vent my wrath on!
When we feel emotional, we ought to direct that in positive directions (help the victim, change the legal system to reduce false convictions, change the police culture) rather than negative ways (hang the perpetrator because I'm angry, dang it! Burn the mayor because it happened under his watch! Smash windows because Hulk smash!).
When we aren't feeling (overly) emotional, and balancing the pros and cons in a purely rational way, that's when we should adjust laws for punishments - bearing in mind all five (or more) of the things we are trying to balance for.
In this situation, are you saying we should raise the statue of limitations for torture, or only for torture-used-by-people-in-authority-to-get-confessions? And if the latter, is that only confessions that are proven false, or does that include confessions that are proven true (e.g. if the confession was for a kidnapping, and the confession correctly revealed the location of a kidnapped child who otherwise would've starved to death in the next few hours)?
It's also difficult to know what the perpetrators truly thought. Did they genuinely believe they had the person who committed murder? If so (and if we had evidence that they truly believed they had a murderer), should that belief reduce their sentence or not? Is torture in the pursuit of safe neighborhoods, puppies, and justice for all worse than, equal to, or less than torture in the pursuit of career advancement and simply reducing paperwork and footwork? Torture is torture, and ought to be punished... but to what extent do we punish it? Is self-interested torture worse than for-justice torture or worse than self-sacrificing torture?
How do we know the hearts and minds of those we are judging? By the very nature of not knowing what the perpetrator was thinking and feeling, and not knowing whether he has genuinely felt remorse, even if we have perfect 100% conviction of genuine guilty people, and perfect 0% conviction of innocent people, ALL laws will over-punish some guilty people and underpunish others, convicted for the same crime.
So, do we give more leeway to judges and let their internal biases have more effect, and let the judges be more open to manipulation by suave criminals and lawyers who are paid to pretty much lie through their teeth (something that's flawed with our system in general - lawyers of the defendants should be required to ensure justice is pursued, not to ensure guilty clients go free), or should we give less leeway to judges, reducing personal judge bias, but maximizing the reality that any law, no matter how fair, is custom-fit to the crime, and not the criminal committing the crime.
Human-guided injustice is imperfect. And will always be imperfect, until we can read criminal minds perfectly - both their present state, and the state of their mind during the crime.
I'm not saying justice was delivered here (I don't think anyone thinks that); I'm saying, it's freakin' hard for the law to deliver justice except in very broad inaccurate strokes.