Employee claims must be taken seriously and adequate resources must be invested by a company in order to protect itself and and everyone involved, especially the complainant. Oftentimes, trying to handle things "internally" within the company backfires because employees do not have the right training and cannot avoid conflict of interests. This sometimes leads to even greater harm to the person(s) who complained and also the company who now has to deal with a lawsuit that could have been avoided.
For example, California law requires employees to take reasonable steps to prevent harassment and discrimination. Companies who knew or should have known of a claim but fail to act exposes themselves to liability. Procedures should also be put in place to prevent retaliation. Having an independent investigation conducted by a neutral third party such an an attorney who has investigation experience may greatly assist to defend against these type of claims.