I bet it was the case you had a glass/drink and 'thought' you'd be safe by the time you came to drive but proved to be just over. Similar has happpend to me when drinking knowing I have to drive soon after - luckily I haven't been stopped, but I now only stick to drinks I know the strength of if I have to drive later. I tend to always have something to eat as well just to help absorb the alscohol and always have a glass of water before leaving. Although the food and water intake might only be marginal in helping 'dilute' the alcohol, I just do it in case it's enough for being 'just over' the limit and just under. Good luck with getting the charge sorted out though - hope they don't make it stick as a full DD charge...
You know, I still can't believe it happened - when I passed my driving test 6 years ago I swore I would never get in a car if I had been drinking and I never did - until 2.5 weeks ago, when I went out for a night out with my friends and a number of circumstances led to me getting in my car at 3.15am and driving along 3 roads before I got stopped. It had been almost 4 hours since I'd had a drink, I'd been walking out in the cold air for 90 minutes and thought the alcohol was out of my system (if I had known I was over the limit, I would never had got in the car) - unfortunately it wasn't.
The stupidest thing was that the only reason I was even near my car at that point in time was because I had arranged to stay the night at my friend's house so that I wouldn't drink and drive! Even worse, when I was pulled over, I had only been in the car for 3 minutes and was less than 100 yards from my destination.
Unfortunately, my urine test results came in today and they were over the limit (although not by much) so I will be charged in a couple of days time and will go to court in about 10 days. I will get an automatic 12-month ban and a fine of anything up to £700!
Hopefully though (as long as I get my visa), I will be leaving the country in 4 months and will be living in the US for 4+ years, so the licence ban will only affect me until Christmas. Also, after I've finished my PhD and return home, the conviction will be just about spent on my record here, so my only major worry will be car insurance costs and lack of a clean licence until 2018.
for the OP - I think you'd need to research this just like Ksand24 is having to do - maybe support it with good character references etc if needs be. You can take the risk of course just like lilmrsmullen says - if the traveller is someone just visiting the US for a holiday and has no ties there etc, then IF they get caught they'll just be not allowed to visit in the future - if you / traveller are someone with ties in the US - always declare as you dont want to be permanently denied entry into the US.
After 2 weeks of research regarding visas, I've come to the conclusion that my DD will hopefully not result in a visa refusal as the only grounds they can refuse on are 'criminal conviction' (moral turpitude or controlled substances) or 'mental disorder and harmful behaviour as a result of alcohol abuse' as assessed by a panel physician. DD isn't considered a CIMT so that shouldn't apply and I don't have a mental disorder or an alcohol problem, so I ought to be fine on both counts (the other annoying thing about what happened to me is that I hadn't had a single drop of alcohol in the 3 weeks before the incident, and I haven't had a drop since).