"The national ID card system is really sort of the ultimate dragnet device, " said Tim Lynch, the institute's director of criminal justice studies.

CNN: Americans mull national ID cards

An examination of 308 studies from the criminal-justice literature, by David Weisburd of the University of Maryland and his colleagues, found that randomised trials were significantly less likely to report positive outcomes than non-randomised studies.

ECONOMIST: Social science

"It's hard to see how a cop will be able to leave the station house without some potential adverse impact on his personnel folder if it all goes into effect, " said Eugene O'Donnell, a professor of police studies at John Jay College of Criminal Justice.

WSJ: NYPD street stop policy's critics seek big changes