Two studies tested the impact of an alibi witness’s relationship to a defendant on the perceived credibility of that witness. In the first study, 291 mock jurors estimated the frequency with which individuals would invent alibis, the frequency they themselves would do so, and the frequency of interpersonal contact among individuals of varying relationships. The degree of relationship between an alibi witness and a defendant remained a predictor of witness credibility when contact frequency was controlled. In the second study, 512 mock jurors were randomly assigned to case scenarios. Skepticism toward witnesses who are biologically or affinally related to a defendant was greater than skepticism toward a socially linked witness. Both studies supported predications from kinship theory and reciprocal altruism.(PsycINFO Database Record (c) 2016 APA, all rights reserved)