Let's consider the purposes of punishment:
- Incapacitation. We want to prevent the person from committing another crime.
- Retribution. We want to prevent circles of retribution by having a third party, the government, handle the punishment.
- Deterrence. We want to convince people not to commit that crime. This includes both the current perpetrator (post-punishment) and potential future perpetrators.
- Rehabilitation. We want to provide alternatives to crime for the perpetrator and to encourage reform.
These are in rough order of the effectiveness of imprisonment, the most common punishment.
Most crimes become less likely as a person gets older. The peak years for many crimes are in the 16-24 age range. Someone who is in their forties or fifties is much less likely to commit new crimes. This is part of why we let criminals out of prison. Because when they are older, they are unlikely to commit new crimes. So we let them out and save the costs of imprisonment. A delayed imprisonment covers less of the incapacitation period and is therefore less effective.
Anyway, arguments against statutes of limitations:
- Reduced effectiveness of incapacitation may still be worth it.
- The closure of retribution may still offer more societal value than harm.
- Punishing more crimes offers a better deterrence.
- Some crimes may not be reduced in likelihood with age.
Arguments in favor of statutes of limitations.
- Old claims can be hard to litigate. Evidence goes away as data is not retained. Statutes of limitations make it easier to explain to victims why the crime won't be prosecuted.
- Statutes of limitations force victims to make decisions about prosecuting. Because victims know that crimes can fade out, they are more likely to prosecute them while they are newer and more likely to succeed.
- Punishment is cruel. We balance that cruelty with effectiveness. For old crimes, the effectiveness of punishment is less and therefore the balance shifts more towards not punishing.
Remember, imprisonment is most effective at incapacitation and retribution. But both of those are much less effective after a delay. In fact, the time when we most want to incapacitate is shortly after the crime. Once passed, that opportunity is simply lost. And if people don't get immediate retribution, their desire tends to fade. Having the option for government-sanctioned retribution is more important than the retribution itself. If someone is thinking, should I prosecute or not, there is less room left for other possible retributions.
Avoiding prosecution can also have the effect of incapacitating. The perpetrator can't afford to commit other crimes because that would put them back in the system. So perpetrators may have to rehabilitate themselves so as to avoid getting caught for the old crime. Fear of prosecution may be as effective as imprisonment. And if they do commit more crimes, even if the original crime is out of the statute of limitations, the new crimes won't be.
Perpetrators also may be more vulnerable. If they go to the police after a robbery or attack, the police may want to take their fingerprints or DNA. And they can't explain why they don't want that to happen. So they may avoid reporting crimes against them. So then that criminal may get away with it too and go on to commit more crimes. If they know about the statute of limitations, they may be able to talk this over with a lawyer and determine if they can report safely.
If someone finds out what they did, they may be vulnerable to blackmail. At least that risk will eventually go away with a statute of limitations.