These wills are created for an ulterior motive which is not the testamentary operation and execution of the will. Rather in most cases, these wills are created for an immoral purpose like acquiring a property that does not belong to the claimant, deceiving someone etc. One of the essential features of a valid will is the intention of the testator. These wills are supplemented with all the necessary documents to duly execute the collateral purpose and not to execute the will according to the testamentary operations.
http://164.100.79.153/judis/chennai/index.php/casestatus/viewpdf/9691: 2007 SCC OnLine Mad 4 : (2007) 2 CTC 152 : (2007) 2 Mad LJ 466 : (2007) 55 AIC 376 (Mad): HIGH COURT OF MADRAS