how is it that we can accept the claim of the guy who says 'I only told you to buy the land because i preffered to deal with you than with the man who stole it from me' when this would be implicating himself as a liar - and as we learn later, we do not accept the testimony of witnesses who put themselves into the category of sinners.
Gidon Schneider, Cambridge, England
Self-implication is in general only a problem with regards to testimony. That is, Beis Din cannot accept testimony from one who is implicating himself.
In this case the person incriminating himself is a claimant. On a basic level he should win, since we know that he was the original owner and the Machzik is not claiming to have bought it from him. The Machzik, who actually has no case since he did not know for sure that the person he bought it from was the real owner (he might be just a thief), wants to build his case on the fact that he got advice to buy the field from the original owner. We reject this evidence because the original owner's claim that "I only told you etc." is sufficient to invalidate the claim of the Machzik.