An effective investigation may include any or all of the following:

• Interviewing current and ex-employees. It may also be necessary to interview people unrelated to the workplace, if they are able to assist with the investigation.
• Verifying all allegations and counter allegations.
• In the event both parties present plausible explanations concerning the allegations, making a decision based on the most probable account of events.
• Standing down on pay one or both parties during the investigation if necessary.