A veterinarian recommended Judge Thomas Cassuto call Scooby to the witness box to see how the animal reacted to a suspect, The Daily Telegraph reported Wednesday.
The dog is believed by authorities to have been with his 59-year-old owner at the time of her death by hanging. Police ruled the death a suicide but a murder investigation was opened at the behest of the victim's family.
The hearing was convened to determine whether enough evidence exists to go forward with the inquiry.
A witness said the dog "barked furiously" when presented with a suspect at the hearing, the newspaper reported.
Cassuto praised Scooby, who was named after cartoon mystery solving dog Scooby Doo, for his "exemplary behavior and invaluable assistance."
A spokesman for the Palais de Justice in Paris said the incident marked the first time an animal has been called to testify in France. He said he was "almost certain" the testimony was unprecedented on the global scale as well.