probative value

 The ability of a piece of evidence to make a relevant disputed point more or less true.  

For example:  In a trial of a defendant for murder, the defendant's dispute with his neighbor (unrelated to the crime) has a no probative value because it provides no relevant information to the trier of the fact.  However, if the defendant's dispute was with the victim, this has a much higher probative value as it could be a motive for the murder.