It is important to be consistent, but it is even more important to be reasonable. You should investigate the circumstances in each case, and also consider any mitigating factors. It is quite possible that an offence (for example, drunkenness) that would merit instant dismissal in one employee (an employee who comes in fighting drunk), would merely merit a reprimand in another (an employee with long service, who comes in somewhat merry after celebrating a family event). If you do end up treating different employees differently for the same offence, however, you do need to be able to explain and justify exactly why. Otherwise, you risk a discrimination claim.
