The more shaky your case is, the more important what you wear is. If you have a criminal record and/or a history of extended travel outside the US during the past 5 years, subjective impressions can determine your fate, so in that event I would suggest dressing as if you're going to a job interview or half a notch down from that (e.g. shirt and tie but no jacket, or an office-worthy blouse and skirt if you're a woman).