Hello and welcome back to Unsolved, everyone! In the past, the cases we have looked at have been almost complete mysteries with few if any suspects and little to no convictions. This week will be something a little bit different, but no less interesting.

In Ann Arbor, Michigan in 1975, there was a sudden wave of VA Hospital patients going into severe respiratory distress without an explanation. Over 5o incidences of suspicious breathing failures were identified during an FBI investigation, and a total of ten patients ended up losing their lives. In one 20-minute-long stretch, three people nearly died of respiratory failure, which made one doctor found suspicious. Dr. Anne Hill, the chief of anesthesiology, was present during this episode and decided to look into the possibility of someone poisoning the patients. She took things into her own hands and hypothesized that they were all being given a muscle relaxant based on their paralyzed state when in distress, and this was proved correct when she successfully administered an antidote to save a patient.

It was eventually determined that the drug used was Pavulon, an equivalent to curare, which was a toxin used by some South American natives to poison their weapons. This medication causes muscles throughout the body to become inactive, which incapacitates the diaphragm and prevents breathing. One of the barriers in this case was that at that point, no test for finding Pavulon in the tissue of a deceased patient existed. To prove a link between the victims, this test needed to be created, so the FBI eventually did so. It was not completely bad for investigators that this drug was used, however. It has very clear effects on the body and no disease has the same properties, so this ruled out any case of natural death immediately. It is also very fast-acting and requires only three minutes to cause breathing failure, which was very helpful in narrowing down a list of possible suspects.

The killer would need to be in contact with each victim very close to when they were discovered by staff to be in need of resuscitation, which lead to the FBI investigation other hospital staff members. Over 750 different workers were questioned, but eventually Filipina Narciso and Leonora Perez were deemed to be the most likely suspects. This was solidified somewhat when two patients identified them to have injected something into their IVs prior to a respiratory stress episode, but neither could testify in court because they passed away before the case went to trial.

At first glance, this case seems relatively straightforward, but it ended up being one of the longest trials in US history for good reason. The women were first indicted on ten counts of poisoning and five counts of murder in June of 1976. Over a year later, the women were found guilty of three counts of poisoning and conspiracy to poison patients. Most of the trouble in the case was due to the amount of circumstantial evidence involved, which is not very easy to prove beyond a reasonable doubt. The nurses also made many contradictions in their cross examinations, which only proved that someone was lying, but did nothing to clarify information about the murders.

There also some political complications in this case. Both of the defendants were immigrants and throughout the entire trial process many accusations of racism were made. This was not without good reason. One man who would have been a witness called the women “slant-eyed bitches”, and thankfully he was not allowed to testify because of this prejudice.

There are few theories about any different possibilities for these murders, but the prosecution’s case was unstable at best. And even if they were correct and the nurses were responsible for those few instances of poisoning, what if there were other accomplices or what if they were framed? Most people consider this case closed, but there is very little evidence that this is true. The poisonings may have stopped in that hospital when the FBI came to investigate, but there was even a case of the same drug being used to poison patients in a New York hospital just one year later, possibly because of the same killer.