A former coworker of mine sent me a link to this story from Arkansas:

They sent out a batch of subpoenas for anyone who had contact with Albert K. Smith while he was jailed awaiting his murder trial. One of those subpoenas went out to 5-year-old Murphy Smith -- Smith's dog, it turned out.

The defendant had written his dog a letter from his cell, and that is how the shih tzu's name got on the witness list.

Prosecutors realized the mistake on Tuesday after the defendant's brother brought in Murphy to answer the subpoena and a deputy would not let them into the courthouse because no dogs were allowed.

Prosecutor Robin Green said she apologized to the brother for any inconvenience, and added: "The dog was friendly enough and probably would have been a very cooperative witness."

I can see that the Arkansas prosecutor's office is really a crack squad that does their research. Don't attorneys generally depose witnesses before a trial anyway? I don't think it matters really... the dog probably could have claimed Owner-Canine privilege and refused to testify.