@Author
Adding and slapping sections under various prevailing laws is the duty & prerogative of Investigating Officer. Complainant has to be true while explaining the complaint and he/she should not intervene into the investigations. However, if you feel that investigators are helping the accused or not taking proper steps for fair investigation, then you may file an application before the Magistrate under proper jurisdiction for transferring the case to other police station or direct the ACP/DCP to personally investigate into the matter.
S.498a is automatically attracted if you have alleged that the in-laws used to harass the deceased girl for dowry. If even after such a complaint this section is not added, then magistrate may add it on his own while accepting the charge sheet. If Magistrate fails to do so, then the trial court, i.e. Sessions Court, after going through the FIR, if prima-facie, a case is made out, shall be pleased to add this section before commencement of trials.
Please note, S.304b of IPC is more deterrent than S.498a of IPC. Your purpose is to punish the accused or to take revenge and rope in all the family members and harass them? Adding sections would only amount to harassment but not justice (if your complaint does not disclose any offence under relevant sections). This is general practice that complainant take help from experienced lawyers or police officers to frame a FIR and ALL possible sections are slapped. But in the end they are not able to prove it in trial court. Such cases leads to a situation in courts that 90% of such cases are FALSE. Why not file a true complaint and let a fair trial proceed and arrive at justice?
//peace
/Saurabh..V