Certified copy of power of attorney

How to get certified copy of Power of Attorney from A.R.A.III Kolkata, West Bengal?

A piece of land has been sold fraudulently. The seller made a sale by giving Power of Attorney (PoA) to some agent to hide his name from appearing on the sale deed and other documents. In this case PoA document can be a clinching evidence to prove the fraud.

Under what provision(s) certified copy of PoA can be obtained by 3rd party? Will RTI work in this case?

Please suggest ways to get the PoA.

Thanks