You assume that the court will automatically believe the defendant’s testimony. That’s not a good assumption to make. The court evaluates all the evidence presented and will decide from what is presented whether he or she believes the defendant’s testimony is credible. If the court doesn’t believe the defendant’s story, the defendant will still lose. Where a person leaves the road and by all appearances cuts through a gas station to avoid waiting at a red light, a self serving statement that the driver intended to do something else isn't likely to be very persuasive. If, however, the driver can present some other evidence in addition to simply his/her self serving statement to back it, his/her chances to win acquittal go up.