3 Answers

After a ticket, forget it. I beat a DUI in New york many years ago by challenging the accuracy of the breathalyser. The unit was only 80% accurate according to the manufacturer if administered under ideal conditions. Most times they aren't. Temperature, barometric pressure, when was unit serviced last. (should be every 6 months max,) A dated sticker is attached to the unit after every service. I requested a jury trial, represented myself and won. My reading was border line. Had I blown three times the limit I would not have had grounds to challenge.

You can buy alcotests, you blow into them and get a reading.Try Boots or a garage, or online.

 In France it is soon going to be a legal requirement to have them in your car.

Don't fret the judge will let you know all that when he sentences you.