Spell out the conditions for a violation to trigger an investigation and hearing. There should be a way to elicit witness statements without sacrificing their safety. An investigation should never be conducted by HR or any established in-house department with conflicted loyalties or a record of uniform management support. The final decisions must be made by a panel of at least three decision makers, never just one, and never entrusted to a manager within the company. Subsequent hostility or interference that follows the filing of a complaint will count as a separate violation by the same perpetrator or a new violation if by a different perpetrator.
Policies ring hollow without enforcement.
They are plastered all over walls in nice frames and fill countless binders. Its enforcement must be seen as free of the typical intervention or political chicanery that shows rules apply to some and not to others. In order for the policy to be credible to employees, however, it must be invoked each time a violation is reported, no exceptions allowed. Built into the system will be a progressive disciplinary system that will allow the bully a chance to change before facing termination. It is just that that bully cannot be around the same target ever again.