The crime of drunk driving is generally defined in two ways: (1) having a blood alcohol content above the limit set by law, or (2) driving under the influence of alcohol. To find a person guilty under the first definition, a jury must be convinced beyond a reasonable doubt that the person's blood alcohol content (BAC) exceeded a certain amount. In most states the legal limit is .10 percent. Therefore, if it is proved that the person's BAC at the time of the incident was .10 percent or greater, he or she can be convicted of drunk driving, regardless of how much alcohol was actually consumed. As a practical matter, one drink would almost certainly not lead to a BAC of .10 percent or greater; generally, a person needs to have five drinks in an hour to develop a BAC of .10 percent. However, if there was something unique about the person or the drink, or other circumstance, one drink could raise the BAC above the legal limit. In contrast, the second definition does not refer to any particular BAC. It focuses on the driving behavior of the person; if it is impaired by the person's consumption of alcohol, he or she can be found guilty of drunk driving. Instead of presenting evidence of the BAC to a jury, the prosecution seeking a conviction under this definition generally presents testimony about the person's driving and consumption of alcohol. A police officer will often describe the impaired driving that lead him to pull the person over and the person's ability (or lack thereof) to perform field sobriety tests, such as walking a straight line. Evidence is also usually presented concerning the person's consumption of alcohol and if the jury then concludes that the prosecution has met its burden of proof, it will convict the person of drunk driving. A susceptible person may exhibit impaired driving after one drink and therefore be convicted of drunk driving.