The authenticity of the copy cannot be judged, and the signature on it will change when copying, so it is impossible to confirm the signature of the other party through technical appraisal.

In addition, the copy is not necessarily without legal effect. Only when the other party does not approve and does not check the original, the copy can not be used as the basis for determining the facts of the case alone.

Legal basis: Some provisions of the Supreme People's Court on evidence in civil proceedings.

Article 50 During cross-examination, the parties concerned shall question, explain and refute the authenticity, relevance, legality and probative force of the evidence.

Article 69 The following evidence cannot be used alone as the basis for determining the facts of a case:

(1) Testimonies made by minors that are not commensurate with their age and intellectual status;

(2) Testimony issued by a witness who has an interest in the party concerned or his agent;

(3) audio-visual materials with doubts;

(four) copies and reproductions that cannot be checked with the original and the original;

(5) Testimony of witnesses who fail to testify in court without justifiable reasons.