Fixer: Colleague with a complaint against them refuses to mediate

How can I resolve the dispute if one party doesn't want to participate?

A colleague in a health and welfare support role at my organisation recently reported the smell of alcohol on a manager’s breath to the senior management team. However, this appears now to have been unsubstantiated, and the employee accused has raised a grievance. But the person who reported this concern believes they were not taken seriously and acted professionally to complain, and does not want to enter into mediation to resolve the matter. What should our HR team do?

Bottom line: you want to bring about a resolution. Other than a smell of alcohol, you do not say what the effects of the alcohol were or whether this was a regular occurrence. And I do not know what your policy says about alcohol at work; some prohibit it completely, others have a level of tolerance. After all there is an obvious difference between a smell of alcohol and being drunk. 

In the circumstances you describe, as long as the colleague who complained initially had genuine grounds to do so and felt the alcohol was either in breach of your policy on this or at a level that might cause an issue, then it would be difficult to challenge their conclusion. And in those circumstances, and whatever feelings you or I may have about the wisdom of the accused bringing a grievance, a mediation meeting is a good idea.

But mediation can only work if both parties are genuinely committed to an outcome. If your colleague does not wish to participate, you should refrain from arm-twisting too strongly to persuade them. A mediation that involves an unwilling participant might make an already tricky relationship even worse. The only circumstances that might change this is where the person who complained initially did so in a vindictive way. In which case, whoever looked at the matter and decided it was an unsubstantiated complaint should have also resolved that as part of the investigation.