Scintilla of evidence rule is a common law principle that a motion for summary judgment or for directed verdict cannot be granted when there exists even the slightest amount of relevant evidence. The matter should then be tried by a jury. Generally, federal courts do not follow this rule. The scintilla of evidence rule has been discarded in nearly all state jurisdictions. However verdicts must be based upon substantial evidence and that evidence must be reasonably believable.
The following is an example of a case law on scintilla of evidence rule :
The "scintilla of evidence rule" means that there must be some evidence arising out of testimony which elucidates the issues of fact and which enables jury to form an intelligent conclusion, but does not authorize admission of speculative, theoretical and hypothetical views. [In re Crawford, 205 S.C. 72 (S.C. 1944)]