I saw your wife

Jack looked over the backyard fence and admired Fred's wife while she sunbathed topless. The next day, Jack corners his neighbour on the driveway saying, "WOI!! I saw your wife sunbathing in the backyard without her top on yesterday." Fred was quite put out over the peeping incident and told Jack he planned revenge. That very evening, Fred noticed that Jack's bedroom shades were up. Upon closer inspection, he notices Jack's wife in the act of performing oral sex. The very next day Fred calls out to Jack, "Hey, Jack, I saw your wife giving you a blow job last night." Jack replies, "DON'T LIE!!! I wasn't home last night."