Remember, you’re responsible for treating like cases alike; that doesn’t mean you’ll necessarily treat everyone the same way. Employee transgressions don’t exist in a vacuum. Sleeping on the job,
for example, may warrant a written warning for a first offense when
committed by an attorney or financial analyst. That same infraction
might warrant a final written warning for a head nurse in charge of
a hospital’s intensive care unit, because such behavior could jeopardize patient care. If committed by an anesthesiologist in the operating room during a procedure, sleeping on the job might justify a
summary discharge.

As you can see, sleeping on the job isn’t the only issue: The
circumstances surrounding the act of sleeping on the job play a crucial role when determining available remedies to ensure that a particular behavior is not repeated. In addition, a first-time offense
committed by a twenty-year employee most likely won’t be treated
as harshly as an offense committed by a new hire during his introductory period.

Finally, from a standpoint of fairness, realize that employees who are disciplined for inappropriate conduct or poor performance often share their concerns with their peers. It isn’t uncommon for ‘‘war stories’’ to be shared, and disciplined employees learn how the company has treated others in the past who engaged in similar conduct. If your response differs greatly from and is more aggressive than your organization’s past actions, realize that you’ll not only have a morale problem on your hands, you may also be legally challenged to justify the apparent inconsistency of your actions. Inconsistent employment actions in and of themselves are not unlawful;
however, if such perceived unfairness occurs against a member
of a protected class, it could be interpreted as discrimination. Be
careful to review your past practices before doling out discipline or
termination. This should become a routine part of your performance
management system.

Taken From : The Hiring and Firing Quention and Answer Book