EVIDENTIARY value of FIR

F.I.R. is a vital and important piece of evidence as it contains the first version of the incident. However, it cannot be treated as substantive piece of evidence as it is neither recorded on oath nor tested by cross examination. But when the informant is called as witness in the Court his former statement (F.I.R.) can be used both for corroborating and contradicting his testimony as per Section 157, Section 161 and Section 145 of the Indian Evidence Act. But it cannot be used as evidence against the informant as it is hit by Section 25 of the Evidence Act.

F.I.R. could be used for corroborating the informant as per Section 157 and Section 161 of the Evidence Act but it could not be used for corroborating other prosecution witnesses or prosecution case in general.
F.I.R. could be used for contradicting the informant as per Section 145 of the Evidence Act but for that firstly, the attention of the informant must be drawn to the relevant portions where the contradiction occurs. Secondly, explanation should be invited and only then defence can rely upon the contradiction.
If F.I.R. is made by accused himself then it could be used as per the normal rules of evidence unless it is in the nature of a confession, as then it will be hit by Section 25 of the Evidence Act. The position of such case has been discussed in detail in Aghnoo Nagesia versus State of Bihar AIR 1966 SC 119:-

Such an F.I.R. is not inadmissible in evidence
If the information is non-confessional then it could be admissible under Section 21
If it is confessional in nature then it will become inadmissible except the portion which will come under Section 27 of the Evidence Act.
In this case, Supreme Court for the first time clarified that F.I.R. will be admissible in evidence as a whole not in parts but with a rider that in case the non-confessional part has no connection with the confessional part then the former will be relevant under Section 18 and Section 21.

F.I.R. by an accused cannot be treated as evidence against the co-accused.

F.I.R. can be used by the informant to refresh his memory under Section 159 of the Evidence Act.
F.I.R. can be used for impeaching the credit of the informant under Section 155 of the Evidence Act.
It can also be used for proving the conduct of the informant as per Section 8 of the Evidence Act.
F.I.R. can be used to identify the accused, witnesses, place and time of occurrence as per Section 9 of Evidence Act.
In certain circumstances, it could also be used as per Section 11 of the Evidence Act.

F.I.R. cannot be used as a primary evidence of the truth of its contents as it cannot be substituted for evidence given on oath. Therefore, F.I.R. itself cannot lead to the conviction of the accused. But in certain circumstances F.I.R. becomes substantive piece of evidence:

Under Section 32 of the Evidence Act
Under Section 6 of the Evidence Act as res-gestae
Under Section 160 of the Evidence Act.

On the basis of the above, it can be concluded that normally F.I.R. is not a substantive piece of evidence but is a public document as per Section 74 of the Evidence Act and its certified copy could be given as per Section 79 of the Evidence Act. However, it becomes a substantive piece of evidence under certain circumstances but S.H.O. cannot give copy of F.I.R. to the accused unless the police report is ready or else he would be liable under Section 27 of the Police Act, 1861.