Object of police or case diaries:
The object of police or case diary is to enable the court to check the method of investigation by the police.
Chief Justice Edge well summarized the object of such diaries in the following words— “The earlier stage of the investigation which follows on the commission of the crime must necessarily in the vast majority of cases be left to police and until the honesty, the capacity, the discretion and the judgment of the police can be thoroughly trusted, it is necessary for the protection of the public against criminals, for the indication of the law, and for the protection of those who are charged with having committed a criminal offence that the Magistrate or judge before whom the case is for investigation or for trial should have the means of ascertaining what was the information, true, false or misleading which was obtained day to day by the police officer who was investigating the case, and what were the lines of investigation upon which such police officer acted. A properly kept special diary would afford such information and such investigation would enable the Magistrate or judge to determine whether persons referred to in the appeal diary, but not sent up as witnesses by the police, should be summoned to give evidence in the interests of the prosecution or of the accused. (19 All. 490).
The use of a police diary may be studied under three heads.— (i) Use by a Magistrate or the court; (ii) Use by the police officer; (iii) Use by the accused.
(i) Use by a Magistrate or the court:
Police diaries should not be treated as evidence in the case. The court should not take statements contained in the diary as the material which would help it to come to a decision of the case. Section 172 (2) limits its use by the court not as evidence in the case but to aid it in such inquiry or trial.
This means that the court is entitled to use the police diary for the purpose of seeking for sources and lines of inquiry and for the names of persons who may be in a position to give material evidence. The court may, on finding some fact noted in the diary, take advantage of this in order to put some necessary questions to the witnesses in the box so as to elicit in evidence the fact which has been disclosed by the diary. The diary cannot be used as evidence of any date, fact or statement referred to therein. It cannot be used for the purpose of testing the evidence of prosecution witnesses by reading the earlier statements of those witnesses made to the police and entered in the diary. The aid which a court can receive from the entries in such a diary is confined to utilizing the information given therein a foundation of questions to be put to the witnesses. The second purpose for which the court may use a police diary is to show contradictions between the statements recorded in the diary by a police officer and the evidence which the police officer is giving in court.
But before using the police diary for the purpose of contradiction, the police officer who made it, the court must allow such police officer to refresh his memory by looking at it in accordance with the provisions of Section 145 of the Indian Evidence Act. The diary cannot be used to contradict any witness other than the police officer who made it. The Magistrate should not use the police diary to the prejudice of the accused. Even if the defence requests the Magistrate to examine the police diary that would not justify him in using it to the prejudice of the accused.
(ii) Used by a police officer:
The court may permit the police officer who made the special diary to look at it for the purpose of refreshing his memory. But such diary cannot be used to enable any other witness to refresh his memory by looking at it.
(iii) Use by the accused:
A police diary is absolutely privileged from inspection by the accused or his^pleader, the reasons being that if the accused were entitled to ^inspect the diary, the police officer while making the investigation would omit from the diary all information which he believed would be injurious to the prosecution. Section 172(3) lays down that neither the accused nor his agents shall be entitled to call for such diaries, nor shall he or they be entitled to see them merely because they are referred to by the court, the accused is, however, entitled to inspect the diary only in certain cases, i.e., when the diary is used by the court for the purpose of enabling the police officer who made it to refresh his memory, or when the diary is used for the purpose of contradicting him, and the provisions of Section 161 or Section 145 of the Indian Evidence Act shall apply. But even in such cases the accused is entitled to see only the particular entry used and so much of it as in the opinion of the court is necessary in that particular matter to the full understanding of the particular entry and no more.
It would be contrary to public for police to allow the accused a wholesale inspection of all the entries in the diary relating to the investigation. Where a police officer uses a police diary to refresh his memory, the accused has a right to have the diary produced and examined by him to the extent mentioned above, but he cannot call for or examine it merely because the court refers to it.