Johnny Dwyer writes about why the US has not prosecuted anyone for the murder of five American nuns in Liberia in 1992. In the 1990s and early 2000s the case was dependent on US policy toward Liberia, and was not a priority. More recently it became a priority, but still there have been no prosecutions:
In April of 2010, [FBI Special Agent Christopher] Locke met with Justice Department attorneys in Washington to learn whether the nuns’ case would be brought before an American court. The Justice Department prosecutors, however, had come across an arcane legal roadblock. The case law surrounding the statute of limitations on federal murder charges was ambiguous. The statute of limitations on federal murder charges had been five years until it was eliminated altogether in 1994. It was unclear, however, whether this change applied retroactively, opening the door to a prosecution’s case becoming invalid if a judge decided the change could not be applied to the 1992 murders. Any indictment ran the risk of extraditing a suspect they believed to be a war criminal to the United States, only to see him let go on a technicality.