The art of chess deduction

 This is NOT a classic puzzle of some mate in X stuff. This is a test to see your reasoning and deduction skills. The story goes like this:

         2 patzers were playing chess together, and suddenly, an UFO full of aliens appeared in the sky and abducted one of the piece they were using on the h4 square! After the aliens were gone, the patzers came out of the closet they were hiding in and decided to continue the game. But, neither patzer remembered what the piece is nor its color that was on the h4 square. So, can you help them to determine what the piece was?

You have the following clues: White is at the bottom and Black is at the top, it is currently Black's turn to move (since the black king will be under attacked), and, although both patzer had played horribly, all the moves they made were perfectly legal.

So, try to become Sherlock Holmes and figure out what the piece was on the h4 square. The first to get the correct answer gets a trophy.

Reference: Smullyan, Raymond (1979). The Chess Mysteries of Sherlock Holmes. New York, United States: Alfred A. Knopf. p29-37. 

i will think about your question but i m just saying this position is illegal to me.what could be the last move white made?how did white rook go to d7?

Black pawn.

this position is perfectly legal and can be achieved by playing from the starting position

white's last move was cxd8=R+ (capturing black bishop) and white bishop was on h4

but, who's bishop was it?

ahh, but what was your reasoning?

thank you.how did you come to conclusion white bishop stands on h4?

i am waiting for a logical explaination on why it was a white bishop

franksmith and dzikus, whoever came up with an explaination first will get the trophy, or if someone else can come up with the solution

I'd give the solution, but it's taken from a book and feel the author (Raymond Smullyan) should be credited.

i will give credit at the end

Once you eliminate the impossible, whatever remains, however improbable, must be the solution.

-SH :)

Black's pawn structure suggest capturing 4 pieces: b7xa6, f7xe6, e6xd5 and d5xc4

The white pawn could come to c7 by capturing 3 black pieces. Bd8 was the last one it captured (it could not be a rook or queen because Kh8 would have been under a check before playing cxd8=R - a major piece would not be able to come to d8 from somewhere outside 8th rank

Since black has 2 knights all his other pieces had to have been captured - thus the piece on h4 must have been white.

Since all the squares where captures by black pawns occured are white there was only one piece that could not have been captured, namely the dark squared bishop

QED

did too many people read that book? dammit

I did not find the solution in any book, just let my deduction engine run on the position and it produced the solution (my old good brain79 processor :D)

there are those engines?

ill be back later and give the trophy

I have one and use it on a regular basis. It really helps me to be a good programmer - sometimes finding a bug in an application only having a user's description is like investigating a complicated Sherlock's case