Barty Jr's motivation.....

[sugaranddixie1]

No: HPFGUIDX 155943

...in teaching Harry's class about the unforgivable curses?  The only 
conclusion I can come to is that he thought that was what the "real" 
Moody would do & so did it to make his masquerade more convincing.  
Maybe he never heard the saying , "Forewarned is forearmed".  Did 
Voldmort order Barty Jr. to show Harry the curses so he (Barty Jr.) 
could report back to LV with Harry's reactions?  Did he think Harry's 
advance knowledge would somehow cause him to freeze up with fear when 
the showdown took place?  Any thoughts?