I think it's Kang-Brown. There were two companion cases that dealt with drug dog sniff searches. One was A.M. and one was Kang-Brown.
It's in one of those cases; there is a brief paragraph on the distinction between the two. Belief is a higher standard. It requires more in terms of evidence and understanding of what has happened. Suspicion is less. It's somewhat as articulated, as suspicion versus a belief, but it's not a scientifically different standard.