Play Dead by David Rosenfelt

"Few can rival attorney Andy Carpenter's affection for golden retrievers, especially his own beloved Tara. After he astonishes a New Jersey courtroom by successfully appealing another golden's death sentence, Andy discovers that this gentle dog is a key witness to a murder that took place five years before.

Andy pushes the boundaries of the law even further as he struggles to free an innocent man by convincing an incredulous jury to take canine testimony seriously. It will take all the tricks Andy's fertile mind can conceive to get to the bottom of a remarkable chain of impersonations and murder, and save a dog's life—and his own—in the process. "

~ from the book jacket