The case cited by Anonymous is quite different in circumstances; there was a huge strike, and a large crowd of workers sabotaged the plant, etc. The strike might have been illegal and/or unjustified. The ratio decidendi of the case is unclear, and no citation of the case is given. This is not usual misconduct and cannot be applied in general.
Requirement for Conducting an Inquiry
The requirement for conducting an inquiry depends on the category of the worker/employee. If he is a workman as defined in the ID Act and if standing orders apply, an inquiry is required before dismissal, however grave the misconduct may be. If he is not (e.g., executive/officer), he may be terminated instantly as per the contract of employment. For a worker, even if his appointment letter says "you may be terminated without notice, etc.," such dismissal is bad in the eyes of the law. If there are no standing orders, and model standing orders are applicable, then an inquiry may be conducted as per the same.
Mostly, managements want to send a strong signal to others by summarily dismissing delinquent workers. In such a case, the option is that the delinquent worker may be instantly suspended pending inquiry and then the inquiry held, and dismiss him if charges are proved. If an opportunity for defending his case is not given, by not holding an inquiry, the risk involved is that he may come back with rejoicing after 5-6 years, sometimes with full back wages, winning the legal battle in a tribunal or court, which is a serious setback to any management. Hence, it is prudent to be patient enough to complete the proceedings, slowly but steadily.
Also, see sec.33 (2)b, whether it applies (for giving one month's wages), which my guru says is the last nail to be put on the coffin of the dismissed employee! Agar marna tho, pyar se maro.