Radar is not the only way to establish someone's speed; there are other ways to "clock" them, such as pacing them in a car, or using predetermined markers (so that by how long it takes to pass from one to another, you can calculate the speed), so if the officer measured your speed some other way in addition to radar, he could use that measurement instead of whatever radar showed.Or if the officer is simply prepared to say in court that you were going 72, they will believe him, not you when you claim the radar gun showed 65 or 68--the court always believes the trained, sworn, neutral (no personal stake in the outcome) law officer over the driver trying to avoid a ticket. So yes, as a practical matter, they could write the ticket for 72.