When GOI is party to a case in SC, who will argue for govt?? My understanding is that AG/SG will argue the case. But my friend belives that, AG just represents the govt, he just pass on the govt stand to the judges. While another advocate appointed by govt argues on behalf of govt. Can some body clarify which version is correct?

Advocate general is the first advocate of the govt of the union. Thus he has the right to appear on any case where the union govt is made as a party. Cases against union govt can be filed by anybody. Cases filed against the union govt are different from cases filed by the govt on others.  When govt files a case against on any individual or company, it can be criminal or civil. If its criminal, then it's called as prosecution. All cases of prosecution are argued by the prosecutors on behalf of govt. Only the govt has the power to prosecute. 

Sir, then, Advocate General could do prosecution at Karnataka HC in Jayalalitha case. What was the need to appoint PP??

AG is not a prosecutor. He is an advocate who represent the govt in higher courts of law. JJ case was criminal. So why will AG appear? ? Prosecutor will do that job and he did.

All advocates are officers of the court. So whichever court heard the case, it asks the local govt to do the prosecution. AG, prosecutors of Karnataka govt are officers of the karnataka high court. So court can ask any of the prosecutors to do the job.

Is it the court’s decision?

Yes. Court will inform the chief prosecutor to nominate the prosecutor. General prosecutors are attached to particular benches. Like court number 5 will have 1 or 2 prosecutors attached. When case comes before it they take over.

Who is a public prosecutor?

All prosecutors are public prosecutors!! 

There is an understanding if the case is not only about a crime but a wrong against the public, the prosecutor is called a public prosecutor !? such a prosecutor represents or argues on behalf of the public at large.

No. Prosecutors are all public prosecutors. When they belong to special agencies they are called special public prosecutors. Like CBI prosecutors are special prosecutors. Each district should have one PP and any number of APP.