It is not uncommon to see situations like this involving one employee making an allegation against another in which the only evidence provided is one's word that misconduct happened. In that situation, an investigator must review the case, determine the credibility of both parties, and determine who is telling the truth. Note that a workplace is NOT a court of law and therefore does not abide by a standard of "proof beyond a reasonable doubt."
Here are several factors that an investigator assesses in determining credibility:
1) Inherent plausibility: Is the account believable on its face? Does it make sense?
2) Demeanor: Does the person seem to be telling the truth or lying?
3) Motivation to lie: Does the person have a reason to lie?
4) Corroboration: Are there witness accounts such as those by eye-witnesses, people who saw the person soon after the alleged incidents, or people who discussed the incidents with him or her at around the time that they occurred? This includes social media posts. Is there physical evidence such as bruises on the resident that corroborates the person’s testimony?
5) Past record: Did the person complained about (PCA) have a history of similar behavior in the past?
If the resident is in a position to speak for him or herself, that could be particularly important, as well as any physical evidence on his/her body.