In more than six years of spying on Muslim neighborhoods, eavesdropping on conversations and cataloguing mosques, the New York Police Department's secret Demographics Unit never generated a lead or triggered a terrorism investigation, the department acknowledged in court testimony unsealed late Monday. The Demographics Unit is at the heart of a police spying program, built with help from the CIA, which assembled databases on where Muslims lived, shopped, worked and prayed. Police infiltrated Muslim student groups, put informants in mosques, monitored sermons and catalogued every Muslim in New York who adopted new, Americanized surnames.