You're opening a can of worms in your workplace investigation if you let a supervisor read an employee's complaint she filed with the human resources department. Unless the supervisor has a legitimate need to know that the employee even complained or any of the details of her complaint, that documentation becomes part of an investigative file to which only certain HR staff and legal counsel should have access.
Complaint Process
Many employee handbooks contain the company's process for employee complaints. Depending on the company structure, some employers prefer that employees go to their supervisor first and if that's not feasible, employees should report complaints to the department manager before going to the HR department. It's prudent to go straight to the HR department in the event an employee can't talk to a manager. Once there, an HR staffer meets with the employee and typically provides information on how the company handles complaints.
Workplace Investigations
Workplace investigations should be held in confidence to the extent possible. Naturally, if an employee complains about sexual harassment, the HR specialist will need to provide each witness with a brief introduction about the complaint before taking the witness's statement. But the HR specialist shouldn't divulge specific details about the employee's complaint and she should never hand over an employee's written complaint for witnesses to review and possibly refute. That includes the employee's supervisor. Employees' complaints become a part of the investigative file and shouldn't be disclosed to anyone who's not on the need-to-know list.
Supervisor Bias
It doesn't matter whether the employee's initial complaint is in writing or whether the HR specialist transcribes the employee's verbal complaint -- the employee's supervisor should be allowed to read it. If the employee complained about the supervisor, then opening up the investigative file to the employee's supervisor could result in retaliation against the employee. Even if the HR specialist takes a statement from the supervisor, she wouldn't disclose everything the employee shared. One of the keys to investigating workplace complaints is receiving information from employees, synthesizing it and then asking witnesses questions based on analytical and critical thinking skills and standard investigative techniques.
Supervisory Action
If the employee complains about another employee, the supervisor may be privy to some details about the complaint, but he still doesn't need access to the written documentation. In this case, the HR specialist can make a recommendation to the supervisor to take action until the investigation is complete. For example, if an employee complains that she is subject to a hostile work environment because of her co-worker's actions, HR might suggest that the supervisor separate the two employees, assign them to different schedules or, in egregious cases, suspend the co-worker until HR makes its final recommendation.
