about exhibit of papers in a case file

If the documents exhibited without sanction and sign of presiding officer then it is open for counsel of accused to object that.

Such documents will not be considered, but presiding officer may sign on it without your knowledge , because it is his mistake

It can be objected but general magistrate/judge did not care about this fact being the Evidence recorded in the presence of Accused and his counsel.  Therefore, take some other defence

It is irregularity. if Document quoted during examination then nothing fetal if not signed by P.O.

there is lot difference between the illegality and the irregularity. the first can not be cured at any stage the second one the irregularity can be cured by the court itself at any stage, which is not fatal. 

The  successor in office can correct the irregularity under Sec 151 of CPC which gives inherent power to the court  and admit the document in evidence

I do agree with Mr. Prabhakar  & Mr. Ravikant that if it has been pen down in examination - chief and in presence of accused or his lawyer than it is mere a irregularity which can be rectified at any time by the then presiding officer. There is no illegality in it.