How are laws enforced after time passes, which can impact the results?

Question

If Person A commits a criminal or civil offense on Day 1, which then becomes lawful on Day 2, can Person A be prosecuted or sued on Day 3 (Day 1, 2, and 3 are not necessarily subsequent days, but happen in this order)?

Also, if Person A is a minor when the offense occurred, but is now an adult, would the person be legally considered a minor or an adult if prosecuted or sued?

If a statute of limitations is shortened, then does the new one apply or the one that existed when the person did the crime/tort?

Note that although I tagged this United States, information on any country would be relevant.

Answer 1

If Person A commits a criminal or civil offense on Day 1, which then becomes lawful on Day 2, can Person A be prosecuted or sued on Day 3 (Day 1, 2, and 3 are not necessarily subsequent days, but happen in this order)?

As a general rule they can be prosecuted but the exactly language of the effective date language in the statute controls. It might say, for example, "effective for prosecutions filed after Day 2" in which case it couldn't be prosecuted.

Also, if Person A is a minor when the offense occurred, but is now an adult, would the person be legally considered a minor or an adult if prosecuted or sued?

Generally speaking, a minor. But this is a function of the language of the statute in question in the case of juvenile prosecutions.

If a statute of limitations is shortened, then does the new one apply or the one that existed when the person did the crime/tort?

Again, it depends upon the effective date language of the statute. Typically, it will apply to suits filed after the effective date.

Answer 2

I'm going to answer this in the opposite way and from personal experience, for the jurisdiction of the England and Wales.

I reported my abuser to the police in 2012, and he was arrested, interviewed and ultimately charged with several offences. After investigation, he was also charged with another 50 offences against another 12 children.

Unfortunately, despite the Sexual Offences Act being updated in 2003, my abuser could only be charged with the relatively minor offence of "Indecent Assault", because the offences occurred in the 1980s - he could only be prosecuted as per the law at the time of the offence, rather than the current law (which would see him charged with the offence of rape under the Sexual Offences Act for several of the Indecent Assault charges).

So in the case of where the law was made harsher between the offence and the prosecution, the charges do not reflect that change.

In the case of where the law becomes more lenient, especially to the point of where the act is now legal, prosecutors would have a hard time justifying a prosecution being within the public interest and therefore the prosecution would almost certainly not happen.

Answer 3

Under Hungarian law, a Continental law jurisdiction within the EU, Person A, by the operation of law, may not be prosecuted on criminal charges on day 2 or day 3 even if the effective date is set for day 4.

The principle is that criminal offenses must be universal, and not subject to change despite the usual reality that legislation changes criminal law. Whenever such change is voted into act, it is considered, merely as principle, as the past interpretation was wrong.

This also means that a change in law allows persons incarcerated to be let free once such decision is made. I personally believe this principle is morally correct provided that any change is done in good faith, and actually serves justice more commonly; however, criminal law changes typically only recognize the heavier or lighter weight of criminal conduct, and will only result in less severe punishments.

In practice, where a exoneration could happen or was reasonably expected that it could have happened was cannabis-use related charges. If the European Court of Justice hands down a ruling that, say, recreational use of cannabis is not criminal that would result in change in Hungarian law, and people would need to be let free. I feel like that could also bring the Hungarian government in the crosshairs of civil law suits, but the likeliness for such to prevail is equal to zero under the Curia or the Court of Constitution, and even at the ECJ, it would be negligible, but these speculations are more in the territory of political discourse.

On the contrary, if Person A's conduct on day 1 meets criminal threshold under law passed on day 2, Person A may also not be held liable even if, following the above moral principle, the act was universally criminal hence it should have been prosecuted yesterday, a civilian is not expected to act in accord with such underlining universalities of moral, but only to comply with the law whatever it may be.

These should hold true in a reliable extent despite the accelerating authoritarian shift at least for the time being.

I could not make an educated guess on whether or not Person A would be relieved on day 3 from civil liabilities from harms that were recognizable under a previous understanding of the universalities of crime.