special pleading

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Law Responsive pleading from a defendant that does not deny the factual allegations of the other party but argues that the defense is entitled to prevail, as in the justification of a killing being prosecuted as murder.
• noun The presentation of an argument that mentions or emphasizes only favorable aspects of the question at issue.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an argument that ignores all unfavorable evidence
• noun (law) a pleading that alleges new facts in avoidance of the opposing allegations