Sources didn’t provide much detail about the way in which officers determined Hart’s level of intoxication. Sobriety tests are often used alongside preliminary breath testing devices to gather evidence of intoxication. The whole goal of gathering this evidence is to be able to show later on in court that the defendant was too intoxicated to safely operate his or her vehicle-that their consumption of alcohol affected their ability to drive to an appreciable degree.
If police gather enough evidence of intoxication upon the arrest, they will typically take a breath or blood sample which is supposed to provide a more accurate reading. If the blood alcohol concentration is above the legal limit, which is .08 in Louisiana and in most states, it is enough evidence to convict the defendant of DUI without a lot of explanation.
Of course, there are some ways in which breath and blood samples may not be completely accurate. This and other issues are part of what defense attorneys look for in evaluating and building a criminal defense case.
Source: The Advocate, “Comedian Kevin Hart arrested on suspicion of DUI,” April 16, 2013