My understanding is as follows:
FIR is first information report that is registered by the police when an informer/ whistle blower reports a cognizable offence to the police. upon and after the registration of FIR police starts investigation and collect evidence. At the end of investigation of there is no sufficient evidence on the complaint/ FIR then the accused are discharged and no further action is taken. Whereas, if there is sufficient evidence available then the arrest is carried out by police and a chargesheet is released on the basis of allegations and available evidence.Now the chargesheet may or maynot have the same offences as listed in the FIR. sections of IPC and either added or deleted by the police at the time of preparation of chargesheet. Hence the sections of IPC listed in chargesheet may vary from that of in the FIR.
Once the chargesheet is ready it is generally submitted to court with evidence collected by the Investigation Officer. This is when its called the case is in court and Judge issues summons to the accused.
The main point to highlight here is that when a chargesheet is submitted in court that reflects that the police investigation is over and the case is ready for framing charges and trial if charges framed. However, either party can call for reinvestigation if they can convience the court that Investigation was not carried out correctly blah blah blah.... Aditionally, once a chargesheet is filed in court the police is generally out of the picture and the case is then handled by the legal counsel's and public prosecutor. So instead of police it the judge and counsel that will try to extort as much as they can from you before the assist you in settling the matter amicably.
Hope this gives you some idea. If i have mentioned anything wrong then please feel free to correct me. I am not an expert but have some understanding of this issue.
I agree with 498406420victim, except those highlighted. Upon investigation if the IO does not find any prima facie, then he/she does not have power to discharge. He will put all his findings in the CS (whether true or false), under crpc 173...
The Code of Criminal Procedure, 1973 (CrPc)
173. Report of police officer on completion of investigation.
(1) Every investigation under this Chapter shall be completed without unnecessary delay.
(2) (i) as soon as it is completed, the officer in charge of the police station shall forward to a Magistrate empowered to take cognizance of the offence on a police report, a report in the form prescribed by the State Government, stating-
(a) the names of the parties;
(b) the nature of the information;
(c) The names of the persons who appear to be acquainted with the circumstances of the case;
(d) whether any offence appears to have been committed and, if so, by whom;
(e) whether the accused has been arrested;
(f) whether he has been released on his bond and, if so, whether with or without sureties;
(g) whether he has been forwarded in custody under section 170.
(ii) The officer shall also communicate, in such manner as may be prescribed by the State Government, the action taken by him, to the person, if any by whom the information relating to the commission of the offence was first given.
(3) Where a superior officer of police has been appointed under section 158, the report, shall, in any case in which the State Government by general or special order so directs, be submitted through that officer, and he may, pending the orders of the Magistrate, direct the officer in charge of the police station to make further investigation.
(4) Whenever it appears from a report forwarded under this section that the accused has been released on his bond, the Magistrate shall make such order for the discharge of such bond or otherwise as he thinks fit.
(5) When such report is in respect of a case to which section 170 applies, the police officer shall forward to the Magistrate along with the report-
(a) all documents or relevant extracts thereof on which the prosecution proposes to rely other than those already sent to the Magistrate during investigation;
(b) the statements recorded under section 161 of all the persons whom the prosecution proposes to examine as its witness.
(6) If the police officer is of opinion that any part of any such statement is not relevant to the sub-matter of the proceeding or that its disclosure to the accused is not essential in the interests of justice and is inexpedient in the public interest, he shall indicate that part of the statement and append a note requesting the Magistrate to exclude that part from the copies to be granted to the accused and stating his reasons for making such request.
(7) Where the police officer investigating the case finds it convenient so to do, he may furnish to the accused copies of all or any of the documents referred to in sub-section (5).
(8) Notwithstanding in this section shall be deemed to preclude further investigation in respect of an offence after a report under sub-section (2) has been forwarded to the Magistrate and, where upon such investigation, the officer in charge of the police station obtains further evidence, oral or documentary, he shall forward to the Magistrate a further report or reports regarding such evidence in the form prescribed and the provisions of' sub-section (2) to (6) shall, as far as may be, apply in relation to such report or reports as they apply in relation to a report forwarded under sub-section (2).
Based on this fact the judge will discharge the case and not the IO.