The first step is to ensure that the traffic stop itself is based on reasonable suspicion or probable cause that a traffic law has been violated, such as speeding, impaired driving, failure to use a seat belt when the law requires it, and defects in the vehicle's safety equipment. Upon making a legitimate traffic stop, an officer may conduct a computer check for outstanding warrants, investigate the driver's sobriety and license status, establish that the vehicle is properly registered and has not been reported stolen, and issue a traffic citation or warning. This routine phase of any traffic stop may be extended into a criminal investigation phase only if certain conditions are met. First, the driver must consent to the continuing intrusion, or information obtained in the routine phase of the traffic stop must warrant reasonable suspicion or probable cause for detaining the driver longer. This may involve requiring the driver to wait for a more extensive computer check or waiting until a K-9 unit arrives with a drug-sniffing dog. 45 notes