Do not confuse empathy with sympathy. Empathy is the capacity to recognize another's reality. It doesn't imply that impartiality is negated. It doesn't trump reason, it informs reason. The Founding Fathers would not have been able to draft the Constitution without it.
Lady Justice's eyes are blindfolded because she is not to be swayed by outside influences; if there was to be no empathy, then instead of scales, her heart and head would be in her hands. If justice did not possess empathy, then we could just have computers interpreting the law.