Brendan Banfield, who is accused of conspiring with Brazilian au pair Juliana Peres Magalhaes to kill his wife, Christine Banfield, and the stranger, Joe Ryan, is a former IRS agent. “Brendan, he has a knife,” his wife cried out, Banfield testified. “And Christine kind of yelled, moaned.”Both Banfield and Peres Magalhaes shot Ryan, police have said. Last week, Peres Magalhaes testified that Banfield was trying to avoid a divorce as their affair developed. The plan, according to Peres Magalhaes, was to tell police they shot Ryan after he stabbed Christine Banfield.