"A vital witness is a witness whose evidence is fundamental, in that it determines the case one way or the other.

Failure to call a vital witness by the prosecution is fatal to the prosecution's case. See State v. Nnolim 1994 5NWLR pt. 345 p. 394.

Furthermore, failure to call vital witness raises the presumption under section 149 (d) of the Evidence Act that had he been called the evidence he would have led would have been unfavourable to the prosecution."

Per RHODES-VIVOUR, J.S.C. in CHUKWUKA OGUDO v. THE STATE
CITATION: (2011) LPELR-SC.341/2010