In Illinois v. Caballes (2005), SCOTUS ruled that:

In Illinois v. Caballes (2005), SCOTUS ruled that:
 
  a. drivers of automobiles have a reasonable expectation of privacy that protects them from the use of drug-sniffing dogs without a warrant.
   b. drug-sniffing dogs can only be used if there is reasonable suspicion the driver has narcotics.
  c. drug-sniffing dog searches are prone to many errors and are so intimidating that officials must have probable cause to use them.
   d. the use of well-trained drug-sniffing dogs to expose contraband items that would remain hidden in a routine traffic stop does not intrude on a driver's reasonable expectation of privacy, and the Fourth Amendment does not apply.