Can we be penalized for not investigating?

Yes! While the gut reaction to serious allegations may be to act quickly, this is most certainly the wrong approach.

For example, making the rash decision to terminate an employee for cause because of their alleged behavior can be incredibly risky. Not only is the cause allegation unlikely to hold up if the employee files a legal claim, but the employee’s lawyer will almost certainly pursue a claim for bad faith, which could lead to punitive damages meant to punish an employer’s bad behavior. This can lead to a significant financial penalty on top of any severance that that employee may be owed. 

If a penalized employee does retain a lawyer, that lawyer will be going through every single detail of the investigation to make sure that it was conducted properly. If there were any steps missed, or skipped outright, they are likely to argue that any discipline of that employee was based on faulty information, and you as the employer should be held responsible. A thorough investigation may have worked in your favour, but a half-baked or sloppy investigation can prove costly.