Plea of undue influence

It is the mother in your case who can testify for being induced to act which otherwise she would refuse to do.

The relationships, dependance and circumstances and the mother's admission may help in seeking cancellation of such gift deed if your mother is having such rights on that property.  Without local advocate, you cannot proceed and first, you have to get such an admission letter from mother before proceeding further.

The donor can file a suit for cancellation of the registered gift deed stating the reasons what she relies upon for seeking this relief.

If it was executed by coercion or force or undue influence, she can produce documentary evidnces for that or rope in witnesses to prove her pleadings. 

Even when the evidence pacca to get a cancellation is very difficult and complicated over a period of time.  The chances to establish undue influence by third party is difficult and left to chance without certain success.

When donor is not alive the gift deed can not be cancelled even if it was executed under coercion.