The mystery witness turned out to be a Shih Tzu

They had been interested in talking to Murphy Smith since the main suspect sent him a letter from his cell.

But when he turned up at court, lawyers knew they had grabbed the wrong lead for Murphy was a pet, not a relative.

Albert K Smith, the dog's owner, is awaiting trial in Arkansas, over the shooting of his ex-wife's boyfriend.

The defendant had written to Murphy from his cell - alerting prosecutors' suspicions.

They sent out a subpoena, and the five-year-old Shih Tzu duly appeared at the Benton County Prosecuting Attorney's Office, led by the defendant's brother.

An official refused to grant them access to the courthouse - because no dogs are allowed.

Prosecutor Robin Green told the Associated Press news agency she apologised to the brother for any inconvenience, adding: "The dog was friendly enough and probably would have been a very co-operative witness."