G = my client is guilty        K = knife was in the drawer
J = Jason saw the knife        O = knife was there on October 10th
H = hammer was in the barn


1.  If my client is guilty, then the knife was in the drawer.

2.  Either the knife was not in the drawer or Jason Pritchard saw the 
                                                                knife.

3.  If the knife was not there on Oct 10, it follows that Jason didn't 
                                                                see it.

4.  If knife was there on Oct 10, then knife was in drawer and hammer was 
                                                               in the barn.
5.  But we all know that the hammer was not in the barn.

n.  GOAL  Therefore, ladies and gentlemen of the jury, my client is innocent.

 1.  G ---> K            hyp      GOAL Prove G'   (Goal to prove: not G)
 2.  K' v  J             hyp                                      -----
 3.  O' ---> J'          hyp
 4.  O ---> (K ^ H)      hyp
 5.  H'                  hyp

 6.  (K ^ H)' ---> O'    4, contra    contrapositive          contra
 7.  (K' v H') ---> O'   6, DM        De Morgan's             DM
 8.  H' v K'             5, add       additive                add
 9.  K' v H'             8, comm      commutative             comm
10.  O'                  7, 9, mp     modus ponens            mp
11.  J'                  3, 10, mp                            
12.  K'                  2, 11, ds    disjunctive syllogism   ds
13.  G'                  1, 12, mt    modus tollens           mt