A former Saugus library aide, declared a psychopath by a Harvard psychologist, was sentenced Thursday to five years in prison for stealing nearly $1 million in library and charity funds to pay her mortgage and dental bills and purchase jewelry and hotel stays.

“One of society’s responsibilities is to pay for our crimes,” US District Court Judge ­Douglas P. Woodlock said in handing out the sentence, as Duffy looked on, looking stoic. “As a society, we have an obligation to say to ourselves, and those who might consider this, that there’s a very serious sentence imposed for something like this.”