The Justice Department is opening a criminal investigation into charges that Republican staffers on the Senate Judiciary Committee improperly spied on their Democratic counterparts by illegally accessing 4,000 internal memos on the computers of Democrats. Some of the memos were then released to conservative media organizations. The Justice Department hasn’t confirmed the investigation, but Senator Patrick Leahy of Vermont announced Monday that Justice has assigned US attorney David Kelley of New York to oversee the investigation.