guiding principle in illegal dismissal

Settled is the rule that in termination cases, the burden of proof rests upon the employer to show that the dismissal is for a just and valid cause. The case of the employer must stand or fall on its own merits and not on the weakness of the employee's defense. 

(pcl shipping philippines, inc. and u-ming marine transport corporation versus national labor relations commission and steve rusel, g.r. no. 153031, december 14, 2006)

case on illegal dismissal

an example of a case for illegal dismissal is nfd international manning agents and a/s vulcanus oslo versus national labor relations commission, jose i. ilagan, jr. and constantino co, g.r. no. 165389, october 17, 2008. the court said, 

The minimum requirement of due process in termination proceedings, which must be complied with even with respect to seamen on board a vessel, consists of notice to the employees intended to be dismissed and the grant to them of an opportunity to present their own side on the alleged offense or misconduct, which led to the management’s decision to terminate. To meet the requirements of due process, the employer must furnish the worker sought to be dismissed with two written notices before termination of employment can be legally effected, i.e., (1) a notice which apprises the employee of the particular acts or omissions for which his dismissal is sought; and (2) the subsequent notice after due hearing which informs the employee of the employers' decision to dismiss him.

(you can find complete text of the case on the supreme court website, lawphil or chanrobles).