Evidence of Investigating Officer could be relied on unless he is discredited in cross examination and found guilty of dishonest investigation. 1992 SCMR 489. Muhammad Usman etc.
Failure of prosecution to examine Investigating Officer deprives the defence of their very valuable right and opportunity of shaking the credit of the prosecution witnesses by bringing out the contradictions between the statements made to the police during investigation and their evidence in the Court. Such  a serious defect could not be cured. PLD 1997 S.C. 408, State v. Bashir etc.
Opinion of Investigating Officer as to innocence or guilt of the accused is not relevant. Courts action in obtaining such opinion condemned. (SC) PLD 1958 SC (Pak.) 275. Moonda. (DB) PLD 1958 Lah. 300. Durgahi.
Opinion of Police Officer is not per se legal evidence but can be considered in granting or refusing bail. Police finding accused innocent. Accused rightly enlarged on bail. 1969 P.Cr.LJ 1111 Wali Muhammad v. Muhammad Akbar.
Opinion of Investigating Officer is irrelevant and inadmissible in evidence when it is about the culpability of an accused and about the innocence of others implicated in the case. 1992 SCMR 2055, Farman Ali etc.
Opinion of investigating officer cannot simply be brushed aside; some weight has to be given to such opinion. PLD 1994 FSC 34, Zulqarnain.
Opinion of Investigating Officer about guilt or innocence of accused has no legal value. (DB) PLJ 1991 Cr.C. (Q.) Noubat.
Investigating Officer not produced, causes prejudice to accused. PLJ 1980 Cr.C. (Lah.) 98. Muhammad Yaqub.
The opinion of the I.O. regarding innocence of the accused. "I found Mehraj Din and Liaqat innocent", being only a personal opinion is not relevant and thus cannot be admissible in evidence as I.O. is not an expert as envisaged by law. The opinion of the I.O. forms part of the case diaries and such views cannot be brought on the record. PLD 1958 Lah. 300, Darghahi etc. referred. PLD 1992 Lah. 314, Haji Muhammad Hanif.
Investigating Officer not examined by prosecution, a serious defect. Retrial ordered (DB) PLD 1958 Dacca 111 A.K.M. Reza. 1972 P.Cr.LJ 649. Muhammad Abbas.
Investigating Officer not examined PLD 1958 Dacca 111 relied on but retrial not ordered. 1972 P.Cr.LJ 1259 Muhammad Sharif.
Non-examination of Investigating Officer and mashirs of recovery, arrest and wardat is a serious irregularity not curable. Revision accepted. PLJ 1991 Cr.C. (Kar.) 200. Suleman etc. = NLR 1991 Cr. 391.
Non-appearance of I.O. as witness in a case had no adversely affected the prosecution case when one Inspector and Sub-Inspector who had signed the recovery memo were eye-witnesses and proved the recovery memo. 1992 SCMR 273, Muhammad Mansha. Also see 1992 SCMR 329, Abdul Majeed.
Investigating Officer bound to see police diary to refresh his memory in the interest of justice, and while refusing to do so renders himself liable to punishment like any other witness. (DB) ILR 23. Lah. 470. Fatnaya v. Crown 43 Cr.LJ 588 = 199 IC 870.
I.O. bound to look into the case diary to refresh his memory to answer questions and if it appears to the Court that the witness purposely suppresses fact the Court may proceed against him according to law. PLJ 1992 Cr.C. (Lah.) 288, Muhammad Shafi.
Secondary evidence to prove hand-writing of I.O. is not admissible unless proved that he was not available or had absconded or was fugitive from justice. PLJ 1987 FSC 28. Muhammad Yamin.
I.O. can be called by High Court while deciding bail matters to question him about merits of the case. 1992 SCMR 1369, Saeed Ahmed Khan D.S.P.