Consider the following scenario.  An employee complains to a supervisor about harassment by a coworker.  The supervisor refers the complaint to human resources.  An HR supervisor interviews the complainant, the harasser, and the witnesses, and instructs the employees to keep everything discussed confidential – a perfectly acceptable instruction, right?
Not so fast according to the National Labor Relations Board (NLRB).  As part of a continuing series of decisions making life more complex for employers, in Banner Health System, 358 NLRB No. 93 (2012), the NLRB ruled that such a request violated the National Labor Relations Act (NLRA).  In Banner Health, the employer utilized a form that contained an instruction to employees that prohibited talking about the investigation.  Additionally, the HR rep conducting the interviews testified that she gave the instruction not to discuss the investigation while it was ongoing.
The NLRB concluded that the employer’s “blanket” rule approach to confidentiality was overbroad and therefore unlawful because it restrained employees from exercising their Section 7 rights to engage in protected and concerted activity (such as discussing workplace misconduct) under the NLRA.
Takeaway:  When conducting an investigation into possible employee misconduct, an employer must make a case by case assessment of whether there is a need for confidentiality.  Issues such as whether witnesses need protection, there is a danger of evidence being destroyed or testimony being fabricated, or a need to prevent a “cover up,” are issues to be considered in determining whether to instruct employees that the investigation must be kept confidential.  Be sure to consult your labor counsel to determine when it is appropriate and lawful to insist upon employee confidentiality.