Establish a protocol
HR departments should have a process for launching and conducting a workplace investigation. Overlooking or downplaying complaints not only hurts employees, but also could warrant lawsuits. Organizations should make their employees aware of laws and policies that they are expected to follow. That communication should also spell out the repercussions for not adhering to them, such as termination, or termination of benefits.
In-house vs. external investigator
While an HR department should be equipped to handle some investigations; sometimes an external investigator is a better choice. When the problem can be resolved quickly, when there's agreement on what happened, or when the HR department has adequate resources, an internal investigation is often sufficient. However, when circumstances are more serious and fairness is hard to guarantee, an external investigation is usually preferred. An external investigation provided objectivity and protects the organization from intentional or unintentional self-bias.
Boost employee trust
Conducting proper and efficient workplace investigations fosters an environment of trust. Employees will feel comfortable reporting any issues the experience, and confident that the problems will be resolved. When employees feel secure in their workplace, productivity and good employee relations flourish.