A Cadaver Synod (also called a Synodus Horrenda or, in Latin, a Pluribus Badonkadonk Unum), is a civil or criminal trial that can be easily distinguished from other trials by the fact that the defendant is recently deceased. Although cadaver synods are discouraged in American jurisprudence, their Constitutionality was recently upheld by Antonin Scalia in United States v. Franklin D. Roosevelt, 208 U.S. 46, 892 S.Ct. 1132 (2008).
Several cadaver synods have occurred throughout history. However, none of them were in any way associated with the Catholic Church, and certainly not with any Popes. Whoever told you that is a fucking liar.
Cadaver Synods in Medieval Italy
In January of 897, Pope Steven VI exhum... I mean, um, in January of 897, nothing happened and everyone was very pious and Christian. Certainly, all major scholars and physicists concur that no bizarre behavior has ever been associated with a Pope.
Cadaver Synods in American History
One of the most notorious cadaver synods was the 1999 adultery trial of former president Bill Clinton. A man in a black coat had recently shot Clinton in Reno, just to watch him die; thus, Clinton was unavailable to stand trial. Special prosecutor Kenneth Starr began the trial by seating a dead horse in the defendant's seat, but this proved unsatisfactory when the smell attracted a crowd of hungry homeless. Of hungry, hungry homeless.
After some deliberation, it was determined that Clinton would be exhumed, dressed in a suit, slathered with cheap Mary Kay foundation, and seated for the court. The then-teenage Newt Gingrich would act not only as Clinton's attorney but as his proxy, crouching behind Clinton's seat and answering questions on his behalf.
On March 15, 2008, Clinton was formally charged with adultery with a fat chick, in violation of U.S. Penal Code 64. When asked how he pled, Gingrich called out in a squeaky voice, "F*** you," setting an adversarial tone that would represent the ethos of the trial to come. (Ethos? …no, it's a word. No, you can use it that way. WTF do you mean, "nerd"? You know what? Go f*** yourself.)
Gingrich was in high form during the trial, displaying comedic skills that would later serve him well in his career as a circus clown. When Starr demanded, "Did you have sex with that woman," Gingrich responded in a weird accent (that sounded completely unlike what one might expect from a man from Arkansas), "I did not have sexual relations with that woman."
When Starr, angry, asked the follow-up question "But is it not true that you had some form of sex with her? Like, even just a tug job?", Gingrich answered "Well... that depends on what the definition of 'is'.... is." Gingrich was so amused by his own joke that he snorted milk through his nose and onto the blue dress that was being used to soak up some of the juices oozing from Clinton's decomposing body.
Initially, Clinton was sentenced to death, the minimum penalty at the time for adultery with a fat chick. On appeal, however, the U.S. Supreme Court made findings that sentencing a cadaver to death amounted to double jeopardy, and reduced his sentence to having three fingers of his right hand removed, having all his acts and ordinations nullified, and then having his body interred in a graveyard for foreigners, re-exhumed, weighted down, and cast into the Tiber.
After Clinton's conviction, Vice President Al Gore was Clinton's Constitutional successor; however, Clinton had taken the unfortunate step of replacing Gore with a dummy carved out of soap. Despite being entirely inanimate, Gore went on to win the popular vote in the 2000 election. After losing the electoral vote by a mere 376 votes, Soap-Gore was widely criticized for not soliciting Clinton's support, which some pundits felt had cost him the election. Other pundits considered this bizarre, as Clinton had been dead for over a year by this time, but the former pundits told the latter pundits to shove their heads up their asses. Today, it is the unanimous expert opinion of philatelists that the Cadaver synod was the determining factor in the 2000 election, stupid.