Every employer confronts it sooner or later. An employee lodges a complaint about work-related misconduct—harassment, theft, violation of a company rule—and you know you need to investigate the situation. But what’s the best way to proceed?

Some complaints require only minimal investigation; disputes and fighting among employees, for example, can usually be resolved informally through talking. Other, more sensitive complaints, particularly those that could lead to an agency complaint or civil lawsuit, require a formal investigation.

When more formal action is needed, here are some guidelines:

Get started promptly. During that first meeting with the accuser, identify the issues. Get all the relevant information you can, such as dates and times of any incidents and names of witnesses; ask for supporting documents. Ask the accuser, also known as the complainant, to put the complaint in writing; this helps eliminate frivolous claims. Let the accuser know there will be a follow-up meeting after witnesses are interviewed.

No deals. Do not agree not to investigate just because the complainant asks for anonymity or confidentiality.

Choose a fact finder. Decide who will conduct the remaining interviews and gather information. This could be someone from the human resources department, a supervisor, or an in-house or outside attorney. Someone from human resources is often the best choice because that person knows the organization and is less intimidating than an attorney. However, you may want to consult with an attorney before starting the investigation, because the information gathered may then be considered privileged. You may also want to have a witness present during the remaining interviews.

Objectivity is paramount. Above all else, the investigator must keep an open mind and not be influenced by personal opinions about the parties involved. The investigator should also understand the substantive law involved and be familiar with any company policies that may relate to the situation.

Interviewing the accused. Interview the accused next. Ask if he or she knows why the accuser might make such an allegation and whether they have had past difficulties. Let the accused know that no conclusion has been reached yet and that there will be a follow-up meeting.

Stopgap measures. Decide whether interim action is needed, such as separating the employees involved or suspending the accused with pay.

Interviewing witnesses. Plan the order of witness interviews and notify the interviewees. If the accused or accuser has spoken to others about the incidents, be sure to include those people as witnesses. Prepare questions beforehand and ask them in the same order, although the interviews may vary somewhat from witness to witness. Get witness statements in writing or take detailed notes. Encourage witnesses to return later if they have additional information.

Confidentiality. Assure everyone that the information they’ve provided will be kept confidential to the extent possible and that there will be no retaliation. Remind witnesses that breach of confidentiality will result in disciplinary measures and can also lead to defamation or invasion of privacy claims.

Reluctant witnesses. Do not detain reluctant witnesses with threats or force, but do remind them of their duty to cooperate. Some interviewees may ask to have a witness present. A union member may usually have a steward present during questioning, and an attorney may be present if criminal investigators have become involved. Otherwise, an interviewee is not entitled to have a witness, although allowing it would not necessarily harm the investigation.

Final interviews. Interview the accuser and accused one more time. Assess their credibility based on such factors as demeanor, which side makes sense, and whether witnesses made conflicting statements.

Wrap it up. Once the investigation is complete, the investigator should write up the findings. Read the findings, then decide on a course of action; have your decision reviewed by the director of human resources. Some employers prefer to have a team of individuals affected by the issues — human resources, security, a manager — read the findings and arrive at a decision together.

Corrective action. Put the decision in writing and give a copy to the accused and the accuser; take any necessary corrective action promptly. Get a signed statement from the accuser acknowledging that he or she knows the steps you have taken. Document the appropriate personnel files. You may also want to make an appeal process available.

Follow-up. If the complaint was found to have merit, follow up with the accuser; find out how he or she is doing. Address any other problems that were revealed during the investigation.

One final note: Remember that government agencies and courts will look at an investigation to see how thorough and fair it was. A proper investigation now can help protect you against legal problems later.