Three people, A, B and C, (each one of whom is either a Liar or a Knight) are brought before a tribunal for a crime that was commited.

The court records have since been partially lost, and it is only known that A testified that C was the guilty one. The testimony of the other people is unavailable.

It is known that as the court found that only one of the people turned out to be a Knight, but that he was also the one guilty of the crime.

Who was it?