Replying to More homework help...does intent matter?

so i have to write my 4th in class English essay tomorrow, and i know that some ns'ers have some pretty good opinions on stuff.... so if you could come up with some quick smart sounding notes on "Does intent matter" then that would be great

for example, some guy built a nuculer power plant to help power the city, but it blew up because some guy messed and it killed a whole bunch of people, does the intent to help matter?

Thanks!