For nearly 15,000 years dogs have lived with and served humankind as companions, hunters, shepherds and most recently detectives. The average canine possesses hundreds of millions of receptors for odors, compared with a few million for humans. Their outstanding sensory endowment – olfaction – makes dogs sought after by law enforcement. And in the last century, the cultivation and harnessing of this ultra sensitive faculty has become a part of many facets of criminal investigation. Ken Strutin’s article surveys select studies, standards and resources about canine scent detection evidence.