Richard Willstatter was quoted in the New York Times discussing material witness warrants:

Because material witness warrants are usually issued with little public scrutiny and are employed behind the scenes in the shadows of the criminal-justice system, it is hard to know how frequently the police and prosecutors use — or abuse — them. The State Office of Court Administration does not track how often judges issue them. And in declining to comment on the lawsuit, a spokesman for the Queens district attorney’s office said the agency did not have any readily available data on their use.

“Because the practice is not out in the open, we don’t hear about them most of the time,” said Richard D. Willstatter, a past president of the New York State Association of Criminal Defense Lawyers.

Read the full article here: https://www.nytimes.com/2017/09/08/nyregion/material-witness-warrants-queens.html