Yes, Ex post facto law is a constitutional doctrine whose importance cannot be understated. Admittedly, my area of expertise lies in intellectual property prosecution and litigation. However, without having time to research the application of ex post facto law, please allow me to explain my reasoning. I always welcome comments and please correct me if I am indeed wrong (I do not practice in criminal law, and thus, I do not come across ex post facto very often...never really).
Ex post facto law is a law that applies retroactively in a way that negatively affects a person's rights. Like criminalizing an action that was legal when it was committed. Ex post facto is strictly forbidden in criminal cases, but not in civil. However, based on my memory of the subject, if the assault weapon laws were ex post facto as you say, then that would be akin to the feds showing up at my door and arresting me for my possession of an assault weapon that I owned back in 1990 and promplty sold in 1991. As I remember it, ex post facto protects me from being prosecuted for something I did years ago that wasn't illegal to do back then but which is illegal today. So you see, I don't believe that the law is ex post facto because if it was, then I could be arrested today for something I owned back in 1990 when it was legal and sold in 1991 (3 years before the ban came into effect). The 1994 crime bill is not attempting to criminalize and arrest people for past actions that were legal when they occured, it is only saying that if you have an assault weopon today, it is now illegal. Again, the distinction is being arrested and in possession of the weapon today, not being arrested today for my act of having possessed the weapon for a brief period 15 years ago (the latter would indeed be ex post facto). Thus, the law is not ex post facto at all. Legislatures are smart people, they don't make careless mistakes such as that. From my memory of the bill, the law says if you have it today, you can be arrested for it today unless you can claim the exception (affirmative defense) of the weapon being manufactured prior to Sept. 1994. And yes, the burden is on the person claiming the exception similar to if not an affirmative defense.
Explanations of affirmative defenses. For example, in defamation cases, falsity is an element of the plaintiff’s case, an in other cases, truth of the matter is an affirmative defense. To illustrate, take Texas where two separate Tx.S.Ct. cases hold this, and neither one mentions or overrules each other. So which is it? We don’t know. What about § 1983 cases (where if the defendant did not act with bad faith, then he is entitled to qualified immunity). Is bad faith an element of the plaintiff’s case, or is good faith an affirmative defense. It has been held as an affirmative defense. The Court said that the statute doesn’t mention bad faith. So it must not be an element of the plaintiff’s case. However, the only problem with this reasoning is that the statute doesn’t say anything about good faith either. This US S.Ct case discussing this (Gomez) basically gave a bad analysis, because we don’t always care who has the knowledge of the element in dispute (see below). We use circumstantial evidence to prove a lot of the elements because we don’t expect the plaintiff, who may have the true knowledge, to just tell the truth. So Gomez only tells that qualified immunity is an affirmative defense. What about an employment discrimination case? Is intent to discriminate the plaintiff’s burden to plead and prove or is it the defendant’s burden to prove no intent. Statutes almost never tell you who has the burden. The defendant would be the only one who knows if he really had intent, but can a plaintiff win an employment discrimination case without proving intent to discriminate? No. It is obvious that congress did not intend for any plaintiff to be able to win an employment discrimination suit just by proving that he was fired because the defendant can’t prove lack of intent. Obviously, the intent to discriminate is the plaintiff’s element and the plaintiff’s burden of proof. Here, defendant has the knowledge about intent, but the element is still the plaintiff’s to prove. (Goes against Gomez.) Thus, the better way to analyze these questions is to look at who the statute was designed to benefit, and then assign the burden of proof to that person. For example, in the §1983 example above, the qualified immunity given if the defendant did not act in bad faith was enacted into law to benefit the defendant, and thus, the defendant should have to prove the lack of bad faith in order to have the benefit of the law. But sometimes this doesn’t work either. Nothing seems foolproof. Another example, when looking at defamation; is defamation intended to stop bad things being said about someone or to stop bad things being said about someone that aren’t true? It is to stop people from saying bad things that aren’t true. (False bad statements.) This leads one to believe that the plaintiff should not be able to recover just based on bad statements, they must be bad statements that are false. Thus, it is the plaintiff’s burden to prove falsity. If truth of the statement was an affirmative defense, it would be much easier for plaintiff’s to sue and win just because something said was bad. And again, that is not what the law was designed to protect. Again, look at insurance claims. Is an exclusion / exception to insurance coverage an affimative defense for insurance companies. There may be a lot of exclusions. If we force the plaintiff to prove that none of the exclusions to insurance coverage apply, then we will be spending a lot of time trying to prove if any of the exclusions apply. Thus, the exclusion must be an affirmative defense if the insurance company wants to use it. In a Texas case, Eckman v. Centennial Savings Bank, the court said that in DTPA claims, if we require the plaintiff to have the burden of proof to prove that they are not only a consumer, but a consumer with less than 25 million in assets, then the plaintiff will be spending a lot of time proving their net worth. Thus, we require the defendant who wants to take advantage of the DTPA exclusion to prove that the plaintiff’s assets exceed 25 million.
So again, the US S.CT case touches on the issue of determining burdens of proof, but the case is a limited holding and is not widely followed (if followed at all). The general rule in the US is to look at who is claiming the exception to the law and have that beneficiary prove that the exception applies to them. So it is my understanding that the law is not ex post facto and that the burden of proof resides with the defendant. This analysis is well established in every state. I know it sucks, and it doesn't seem fair, but for laws to have effect, it cannot always be "innocent until proven guilty."
