Gift deed

Dear SIRS, My father under duress had given his share in the house to my sister [Half share was in my sisters name] through a Will in 2008. After couple of months he cancelled this Will and given his share to me through an unconditional registered gift deed with his free will. Now, as instigated by my sister, he has now turned against me and filed case against me stating that the Gift deed was done without his free will and while registering the document it was not read out to him and thus I got the gift deed signed by him fraudulently and some signatures were fake and signed by me. Will this case stand in the court? Can I call the witnesses who signed during registration? does he have chance in the court? Can I ask the signatures to be examined by forensic or experts? My reputation and integrity is at stake now. Would highly appreciate your reply. Regards, Alwin