"x x x.
Before proceeding to the discussion on why the petitioner’s contentions fail to convince, it is appropriate to restate here the law of the case doctrine in light of respondents’ erroneous appreciation of the same.
In Padillo v. Court of Appeals,[9] we had occasion to explain this principle, to wit:
Law of the case has been defined as the opinion delivered on a former appeal. More specifically, it means that whatever is once irrevocably established as the controlling legal rule or decision between the same parties in the same case continues to be the law of the case, whether correct on general principles or not, so long as the facts on which such decision was predicated continue to be the facts of the case before the court. As a general rule, a decision on a prior appeal of the same case is held to be the law of the case whether that question is right or wrong, the remedy of the party deeming himself aggrieved being to seek a rehearing.[10]
The concept of law of the case was further elucidated in the 1919 case of Zarate v. Director of Lands,[11] to wit:
A well-known legal principle is that when an appellate court has once declared the law in a case, such declaration continues to be the law of that case even on a subsequent appeal. The rule made by an appellate court, while it may be reversed in other cases, cannot be departed from in subsequent proceedings in the same case. The "Law of the Case," as applied to a former decision of an appellate court, merely expresses the practice of the courts in refusing to reopen what has been decided. Such a rule is "necessary to enable an appellate court to perform its duties satisfactorily and efficiently, which would be impossible if a question, once considered and decided by it, were to be litigated anew in the same case upon any and every subsequent appeal." Again, the rule is necessary as a matter of policy to end litigation. "There would be no end to a suit if every obstinate litigant could, by repeated appeals, compel a court to listen to criticisms on their opinions, or speculate of chances from changes in its members." x x x.[12]
The law of the case doctrine applies in a situation where an appellate court has made a ruling on a question on appeal and thereafter remands the case to the lower court for further proceedings; the question settled by the appellate court becomes the law of the case at the lower court and in any subsequent appeal.[13]
Contrary to respondents’ assertion, the law of the case doctrine does not find application in the case at bar simply because what was involved in G.R. No. 149534 was a criminal proceeding while what we have before us is an administrative case. Although both cases possess a similar set of facts, allegations and arguments, they do not serve the same objectives and do not require the same quantum of evidence necessary for a finding of guilt or conviction/liability which makes them entirely different cases altogether and, therefore, beyond the purview of the legal principle of law of the case.
In administrative cases, substantial evidence is required to support any finding. Substantial evidence is such relevant evidence as a reasonable mind may accept as adequate to support a conclusion. The requirement is satisfied where there is reasonable ground to believe that the petitioner is guilty of the act or omission complained of, even if the evidence might not be overwhelming.[14] While in criminal cases, the accused is entitled to an acquittal, unless his guilt is shown beyond a reasonable doubt.[15] Proof beyond reasonable doubt does not mean evidence that which produces absolute certainty; only moral certainty is required or that degree of proof which produces conviction in an unprejudiced mind.[16]
x x x."
