Any ex post facto problem here?

Congress passes a law in, say, 1970 that makes it a crime to punch postal carriers, punishable by up to five years in prison if convicted. On Dec. 23, 2011, Dave Defendant punches his postal carrier, Vivian Victim, for delivering another thirty Christmas catalogs to him after he’d repeatedly asked her not to. Defendant is indicted on Jan. 1, 2012. On Feb. 1, 2012, Congress increases the penalty for the crime, making it punishable by up to fifty years in prison. On March 1, 2012, Defendant is convicted. The Assistant U.S. Attorney tells the court that the Government wants Defendant sentenced to the full fifty years in prison.

Punching a postal carrier was a crime all along; is there any constitutional problem if the potential penalty is made more severe between indictment and sentencing? How about if it happens between commission of the crime and indictment?

There certainly would be if the case arose in Canada. The Canadian Charter of Rights and Freedoms addresses this very point:

Exactly what I was thinking, Northern Piper. But you beat me to it.

Wikipedia says yes:

An ex post facto law … or it may change or increase the punishment prescribed for a crime…

It has links to many specific countries therein depending on what jurisdiction you’re interested in.

There is some gray area here.

For example, various sex offender registry laws have been retroactively applied. In Smith v. Doe (2003) the Supreme Court ruled that since the registries were “nonpunitive, its retroactive application does not violate the Ex Post Facto Clause.” The ruling was 6-3.

And this is how states have been able to pass increasingly onerous restrictions on sex offenders, even ones convicted before the new rules are in place, and even ones who otherwise had completed their original punishment.

I believe there has been some trend recently of state courts changing their minds on whether they’re punitive.

This may be relevant. A friend had a DUI, went to trial, was found guilty. Paid his fines, spent his days picking up trash. Slept in a jail cell over night. Went to his “Be a better citizen classes.” When all that was done, he still had a note on his license of 0% alcohol if stopped in the 5 years following. Eight years later, he was stopped with a BA of 0.03, less than 1/2 the legal limit. He was taken to jail. He went to court. He even got a lawyer. The court said that the law had changed to 10 years, before his probation was up, so it was automaticly extended.

The South African Bill of Rights has a very similar provision - unsurprisingly, given that it is significantly inspired by the Canadian Charter:

Thanks. The hypo made it clear, I hope, that this would be in the U.S. Anyone have a U.S. cite?

Cite when I get home, but yes, it’s an ex post facto violation in the US.