Here is list of the Ingersoll factors that a court will use in evaluating a DUI check point:
Sobriety checkpoints must be set up along these established guidelines. A sobriety checkpoint must be announced to the public in advance and set up by command law enforcement officers, not officers in the field. Vehicles must be selected using a neutral mathematical formula, and the checkpoints must be maintained safely for both police and motorists, have high visibility, and minimize the average time each motorist is detained. Each motorist who has been stopped should be detained only long enough for the officer to question the driver briefly and to look for signs of intoxication, such as alcohol on the breath, slurred speech, and glassy or bloodshot eyes. If the driver does not display signs of impairment, he or she should be permitted to drive on without further delay. If the officer does observe signs of impairment, the driver may be directed to a separate area for a field sobriety test. At that point, further investigation must be based on probable cause, and general principles of detention and arrest would apply. The Supreme Court has ruled that the primary purpose of a sobriety checkpoint is not to discover evidence of crime or to make arrests of drunk drivers, but to promote public safety by deterring intoxicated persons from driving and endangering the public. Thus, a sobriety checkpoint roadblock serves a regulatory purpose and is not considered a criminal investigation roadblock, and thus no warrant is required. The Supreme Court also stated that motorists who seek to avoid a roadblock may not be stopped and detained merely because they attempted to avoid the roadblock. However, if the motorist commits a vehicle code violation or displays obvious signs of intoxication, there is adequate probable cause to pull over the motorist, after which point general principles of detention and arrest apply.