What if evedence is suffering from parkinson/ memory loss

Law do not know what he is suffering from.

If he is not giving proper reply and if he contradicts his own statement then you can present strong argument, the court will decide the case on merits.

Person suffering from Parkinson' has to prove agreement void/forged/incomplete by other cogent evidence like experts opinion regarding  signatures. 

I appreciate the view of the expert T. Kalaiselvan, Advocate (Advocate) but I also wish to add my opinion on this query. The Indian courts have idntified as many as more than 21 different kinds of witnesses, and the Indian Evidence Act  provides that all person are competent to testify subject to the satisfaction of the court that the witness is competent to testify. This witness is important to the case but at the same time he suffers from memory loss, and there is no use to rely on his statements. Question is how to resolve this Conundrum in the court. The only way forward for the judge is to fall back on the Realist jurisprudence by skiping the formal law and take inspiration from the human factor, and resolve the issues between the parties.

Would like to add that aggreement is initially incomplete with no witness signature but opposite side want to prove otherwise with just the seller signature with cross examination. Seller has already rejected in court for first hearing that the aggreement to sell was forged but not available for cross examination due to Parkinson or Parkinson or health issues.

In a sale deed witness is not necessary, except in the case of Gift deed and Mortgage etc. In the case in hand the seller is avoiding the sale deed and his statements is recorded but incapaciated for cross examination due to parkinson disease, and it is not certain when he will be available for cross examination. The only way forward is to fall on the realist, or wait till eternity, and that depnds on the wisdom of the Judge.

Here conflict is not about sale deed but aggreement to sell portion of farm land without witness as also against government rules not to sell government allocated farm land.

Seller do not want to sell the land since aggreement to sell itself was against government rules but now that government restrictions is lifted, buyer wants to seller to continue with the process.

Since the matter is now in the court, hire a lawyer and resolve the issue or issues with the erudite acumen of the Judge. All the best.

Parkinson desease is not known to be assciated with memory loss. 

First file suit and take GPA to lead evidence who is suitable .