Dismissal Due to Misconduct
The extent to which misconduct may be relied upon to justify dismissal may well depend on a number of factors including whether the incident or conduct arose during or outside employment.
Conduct during Employment
Whether dismissal may be considered to be fair when based on misconduct during employment (e.g. breach of company rules, disobedience or indiscipline) generally depends on the gravity of the offence.
At one end, trivial misconduct initially may be best handled informally, only proceeding through the warning procedure if the conduct is repeated. At the other extreme, most serious gross misconduct (theft, dishonesty, indecency, etc.) may justify instant dismissal without notice, particularly if you specifically state in the employment contract, disciplinary code and/or works rules that immediate dismissal may follow such a transgression (although this is not conclusive).
Conduct outside Employment
Whether such conduct may be considered to justify dismissal depends largely on whether it has an adverse effect on your business or causes you or his colleagues or your customers and clients to lose confidence in the employee concerned.
If there is police involvement, it is not necessarily unfair to dismiss prior to the criminal trial where there has also been a breach of other company rules which would itself justify dismissal.
All misconduct allegations should be carefully investigated and it may well be advisable to take advice as to the level of action that may be appropriate in response to misconduct (ie. whether to dismiss either with or without notice; whether to give formal or informal warnings; or to take other action).
A fair procedure observing the principles of natural justice should be followed at all times.