Animals cannot serve as witnesses in a courtroom, as they are unable to understand the difference between lying and telling the truth and cannot be sworn in under oath. Humans and animals cannot effectively communicate, except by means of wildly unreliable body language, which is open to broad interpretation. The only purpose a pet could serve in a courtroom is as evidence of abuse or as a means to calm and relax human witnesses.
Pets cannot serve as witnesses in the courtroom. A pet is an animal, not a human that can give testimony in a court of law. There is nothing that a pet could contribute to a court case. Therefore, it makes no sense to call a pet as a witness in a trial. Doing so would be grounds for a mistrial.
How could a pet serve as a witness? The thought of this sounds absolutely ridiculous to me. I understand that some animals have special senses, and it is possible that a pet may recognize an offender. However, I don't think an animal - any kind of animal - could actually provide any reliable information.
Allowing a pet to be a witness in the courtroom is a completely ridiculous notion. Pets are not able to be witnesses. They are not able to talk or communicate specific facts or events. Facts are what cases in the courtroom should be based on. Animals cannot relay any facts, or any words at all.