According to news reports, 19 individuals were arrested for driving under the influence at DUI Checkpoints in San Diego County on June 7, 2014. Pacific Beach, where the checkpoint was located at the 2700 Block of Garnet Avenue, netted the highest arrests with 16. This should come as no surprise, considering it was a Friday night between 11:00 pm and 3:00 am. This checkpoint was conducted by the San Diego Police Department. There are strict guidelines that must be followed in order for checkpoints to be constitutional. The United States Supreme Court has ruled that sobriety checkpoints are not a violation of the 4th Amendments protection against unlawful search and seizure as long as certain guidelines are followed. 18 states across the country have departed from the United States Supreme Court analysis and explicitly ruled that these checkpoints are not what the founding fathers envisioned and declared checkpoints illegal.
An additional checkpoint was conducted by the National City Police Department which netted 3 driving under the influence reports. However, two of the three were for driving under the influence of drugs, not alcohol, which would be Vehicle Code 23152(a). How were the police able to determine the individual was under the influence of drugs in the brief time that is supposed to be allowed to determine the sobriety of the individual? In my experience, the officers will bases their initial suspicion on bloodshot eyes, or in the case of Marijuana, an odor of marijuana coming from the person and/or vehicle. This will always lead to further investigation. But, since it is normally a blood test that determines drug use, which will not be conducted on the side of the road, it can be very hard for the police to establish enough probable cause to effectuate an arrest.
In my experience as a DUI Attorney, the number one factor they use to determine whether the individual was driving under the influence of drugs, and one of the most powerful pieces of evidence used in these cases: the driver admitted it.