This incident may not have happened exactly as listed, but that's not the point. For the purpose of this question, we'll assume it did. During World War II, The scientists at the Manhattan Project wanted to know how certain radioactive chemicals are metabolized. They designed an experiment in which they took several terminally ill patients and injected them (or fed them) lethal doses of the radioactive chemicals. The excrement of the patients was monitored. The rationale behind this experiment was the subjects' illnesses would kill them before the chemicals anyways, so they weren't really doing any harm.
So what is the halachic view of this? Could a Jew be part of this experiment? On one hand, they were expected to die anyways, so the radioactivity wasn't likely to kill them. And if you'll say they could've recovered through some miracle, then they could also be saved from the chemicals by a miracle! On the other hand, you could also say that scientists don't really know how long someone will live, and you can't needlessly inject toxic chemicals into yourself.