Normand, J.

 1. The objection to the conviction founded on the failure of the police witnesses to keep a diary as required by Section 172, Sub-section 1, of the Criminal Procedure Code may be conveniently disposed of first. It was contended by learned Counsel for the appellant that the evidence of the officers was inadmissible. This contention was not supported by reference to the statute or to authority, nor was it the view taken by the magistrate. In the opinion of their Lordships a contravention of Section 172 lays the evidence of the police officers open to adverse criticism and may diminish its value, but if does not have the effect of making that evidence inadmissible.

 2. The next question concerns the effect of Section 162, Sub-section 1, of the Criminal Procedure Code, which provides that no statement made by any person to a police officer in the course of an investigation shall, if reduced into writing, be signed by the person making it; nor shall any such statement or any record thereof, whether in a police diary or otherwise, or any part of such statement or record, be used for any purpose (saving certain exceptions not material to the present proceedings) at any inquiry or trial in respect of any offence under investigation at the time when such statement was made. It was submitted for the appellant that the proceedings were entirely vitiated and, alternatively, that Mr. Roys evidence was rendered inadmissible, for either of two reasons: first, because he had previously given a signed statement to the police, and, second, because in giving his evidence he made use of the signed statement to prompt his memory. On the other hand, it was argued for the respondent that a contravention of Section 162, Sub-section merely affected the value of the evidence, and that the High Court had taken the correct view of its effect in the present case. It appears to their Lordships that the effect of a contravention of the section depends on the prohibition which has been contravened. If the contravention consists in the signing of a statement made to the police and reduced into writing, the evidence of the witness who signed it does not become inadmissible. There are no words either in the section or elsewhere in the statute which express or imply such a consequence. Still less can it be said that the statute has the effect of vitiating the whole proceedings when evidence is given by a witness who has signed such a statement. But the value of his evidence may be seriously impaired as a consequence of the contravention of this statutory safeguard against improper practices. The use by a witness while he is giving evidence of a statement made by him to the police raises different considerations. The categorical prohibition of such use would be merely disregarded if reliance were to be placed on the evidence of a witness who had made material use of the statement when he was giving evidence at the trial. When, therefore, the magistrate or presiding judge discovers that a witness has made material use of such a statement it is his duty under the section to disregard the evidence of that witness as inadmissible. In the present case there is in the note at the end of Mr. Roys examination-in-chief and in the judgment of the magistrate what amounts to a finding of fact that Mr. Roy while giving his evidence made substantial and material use of the signed statement given by him to the police, and the magistrate was accordingly bound to disregard his evidence. The magistrates reason for doing so is too broadly stated, for it is not the mere fact that Mr. Roy had signed the statement but the fact that he had it before him and consulted it in the witness box that renders his evidence incompetent.

 3. It follows that in the opinion of their Lordships the learned judges of the High Court erred in law when they treated Mr. Roys evidence as admissible. Section 537 of the Code of Criminal Procedure, to which they made reference, requires a Court of Appeal, subject to the earlier provisions of the statute, to affirm, an order of a court of competent jurisdiction where there has been an irregularity in the proceedings unless the irregularity has in fact occasioned a failure of justice. The section cannot apply to a case like the present, in which the magistrate has refused to overlook an irregularity and has acquitted. The further observations of the learned judges that there was no substantial reason to think that Mr. Roys evidence unaided by the written statement would have been in any material point different from the evidence which he gave, and that no real prejudice was caused to the appellant by the use of the statement, are in the opinion of their Lordships unfortunate and ill-founded. It is impossible to say what Mr. Roys evidence would have been if he had not used the statement to aid his memory; and it is also impossible to say that prejudice may not have been suffered by the appellant. But the conclusive answer to the reasoning of the judgment is that the language of the statute clearly prohibits any such use of the statement, and it must receive effect.

 4. It was argued for the respondent that even without Mr. Roys evidence; there was a sufficiency of other evidence accepted as trustworthy by the learned judges of the High Court to justify the conviction. While it is true that the police evidence taken along with the evidence of Bhattacharjee is relevant to infer the guilt of the appellant, that evidence is contradicted by other witnesses, and it has been the subject of adverse comment by the magistrate. It is possible, also, that the High Court would have treated the evidence of the police and Bhattacharjee with less respect if it had not had Mr. Roys evidence before it. The judgment of the High Court largely depends on his evidence. It could therefore be neither logical nor fair to affirm the order of the High Court, while holding that the court erred in taking Mr. Roys evidence into consideration. On the other hand, the submission for the appellant that the acquittal by the magistrate should at this stage be finally re-affirmed would have been appropriate if the irregularity which has taken place had the effect of vitiating the whole proceedings, but it is too favourable to the appellant on the opinion which their Lordships have expressed on the effect of Section 162. The appellants complaint that the High Court had failed to have due regard to the principles laid down in Sheo Swamp v. King-Emperor (1934) L.R. 6r I.A. 398 would have had greater force if the High Court had not believed itself entitled to rely on the evidence of Mr. Roy, and without that evidence these principles will manifestly have a special relevance to the circumstances of the case.

 5. Their Lordships consider that the fair course is to allow the appeal to the effect of setting aside the order of the High Court, and to remit to the High Court to re-hear and determine the appeal on the evidence in the case subject to a direction to exclude from consideration the evidence of Mr. Roy and to deny it all effect. Their Lordships will humbly advise His Majesty accordingly.