Dealing with suspects of sabotaging experiments

Question

In a group, postdoc A believes postdoc B sabotaged her experiments. A shares her frustration with the PI (without proof) in a "half-jokingly, half-serious" sense. Since then, strange things appear to be happening in the lab -- specifically, B's experiments are behaving strangely. There has been a serious decline in trust between A and B.

How should the two postdocs proceed? Should they meet? Should the PI mediate between the two? Should the PI talk to them separately? Or together?

Ultimately, how should the PI address the problem, knowing that an investigation is in practice impossible and with the goal of reestablishing a minimum level of mutual trust?

EDIT: Pushed by the PI, the 3 actors openly talked about these issues, agreeing that sabotage is extremely serious, but without pointing the finger to anyone. That seems to have released quite a lot of pressure and helped to normalized the situation. Hopefully it will last.

Answer 1

That would be the time for the PI to call a meeting with A and B and have a conversation among adults. Topics to be discussed are: If A has a grief with B, she needs to be specific and put it on the table. If B suspects A, he needs to do the same. PI needs to say that this is unacceptable and that everyone needs to behave like adults or else.

If the PI does not call this meeting, then either A or B need to be the grown-up in the room and do so.

Ultimately, half-truths, allegations, conspiracy theories, "experiments not working well", etc, is a situation that is to nobody's benefit. The only way to address it is to talk about it.

Answer 2

Because there is no evidence, then everything radical is out of the question. PI cannot fire them. Sabotaging is really bad thing, and something must be done. Revenge sabotage is almost as bad as the first sabotage.

A has first accused B, but there is no proof, it could be that she just used B to went up frustration over her own failures. "half-jokingly, half-serious" sense sometimes is sign of conspiracy thinking and that there might not be any too good of a reason to believe in sabotage, but she has made the connection within her mind, so the perspective becomes biased and she sees more signs and so on... I do not know if you can see from the results of the experiment something, like if A had small failures, but B clearly has odd stuff happening. A's "revenge" could be B sabotaging own experiments to make A look bad. I do not know about prior relation between A and B, which might be the cause to the mess.

Building up a trust is almost impossible, especially if it is clear that someone has done something. Odd stuff happening around B might count as that something. They are already adults, so I do not think that an adult telling "kids" not to be such fools would work. Nice chat about promising future research in a different department that matches better the research interest of A or B might be in a place.