Roommate disputes can have some pretty gruesome consequences, but there is one case from 1970 in which one man was accused of using his research against his hated roomies. His weapon: Ascaris suum, the parasite that he was studying in school and which he allegedly used to make his roommates very ill.
Discover Magazine points us to this disturbing case from 1970. Eric Kranz, an American student studying parasitology at Macdonald College in Montreal, was asked to leave his house by his roommates when he fell behind on his rent. Allegedly, he responded by threatening to put the parasites he was studying in their food. And sure enough, a few days before Kranz left the house, his four roommates became seriously ill, with two of them nearly dying. With the help of a professor at the Macdonald Institute of Parasitology, the physicians eventually diagnosed the problem: an infestation with Ascaris suum. In fact, each roommate was infested with 300,000-400,000 larvae, which can attack the liver and interfere with the workings of the respiratory system.
Kranz was charged with attempted murder, although he was eventually acquitted. The judge ruled that the prosecution had not eliminated the possibility that the roommates' food had become contaminated in some other way, perhaps due to a recurring sewage backup in the house's kitchen sink.
An interesting aspect of this case is that it's actually the baseline case for Ascaris suum in humans. The nematode causes ascariasis in pigs, but Kranz's roommates were the first known humans to be infested with the parasite.
Photo of Ascaris suum by Alan R Walker, licensed under a Creative Commons Attribution-Share Alike 3.0 Unported license, via Wikimedia Commons.