Arlo, plagiarism doesn't, according to the various public definitions, depend on intention.  There is no distinction - formally speaking - between sloppiness and plagiarism.  This has already been discussed, about a week ago ("manslaugher vs. murder").

This is an error that people make about copyright too.  "For scholarly purposes" means nothing, under the law.   Breaching copyright means physically ...making...a...copy.  It doesn't matter why.  If you copy something physically, without permission, you've breached the copyright-holder's rights.  It's Act, not Intent. 

Best,

Dominik