The Officer/Trooper merely needs to establish probable cause, a subjective reason, to believe that someone is operating under the influence of alcohol.  Since the standard is subjective it is a very easy standard to meet as far as the decision to arrest or charge an individual with Operating Under the Influence of Alcohol or Drugs.  Should you require a consultation from a Board Certified OUI lawyer please feel free to contact Attorney Milligan at 617-851-7155.