Paul Callan is a CNN legal analyst, a former New York City homicide prosecutor and currently is of counsel at the New York law firm of Edelman & Edelman PC , focusing on wrongful conviction and civil rights cases. Follow him on Twitter @paulcallan. The opinions expressed in this commentary are his own.

(CNN) Ordinarily, there is nothing unusual about a defense lawyer seeking an immunity deal in exchange for his client's cooperation.

When, however, the client is the former national security adviser to the US president , the situation is highly unusual. He stands next to the president with a duty to safeguard the nation and its secrets. If he seeks immunity to tell the truth, the country has the right to know why.

On Thursday night, a prominent Washington criminal defense attorney, Robert Kelner, issued the following statement on behalf of his client Gen. Michael Flynn , former national security adviser to President Donald Trump:

"Gen. Flynn certainly has a story to tell, and he very much wants to tell it, should the circumstances permit. ... No reasonable person, who has the benefit of advice from counsel, would submit to questioning in such a highly politicized, witch-hunt environment without assurances against unfair prosecution."

The attorney's carefully worded statement clearly implies he is looking to negotiate what lawyers call a "Queen for a Day" proffer agreement with federal prosecutors and congressional investigators. In the legal profession, the sardonic "Queen for a Day" description of such an important process is a form of gallows humor deriving from the name of a popular television show , whose heyday was from 1956 to 1964.

Such an agreement permits the witness to trade his or her story for a grant of immunity against future prosecution. The "Queen for a Day" part of the transaction arises from the dance that precedes the more formal immunity grant and possible deal.

Prosecutors are not going to trade away their ability to lodge criminal charges against a potential defendant without a meticulous vetting of the reliability and usefulness of the information he or she seeks to trade.

In the "Queen for a Day" debriefing, the client appears with his attorney and answers detailed questions about the information he proffers. Often, FBI agents and multiple prosecutors put forward questions to test the truthfulness of the witness and the value of the information.

JUST WATCHED Democratic congressman slams Flynn's immunity proposal Replay More Videos ... MUST WATCH Democratic congressman slams Flynn's immunity proposal 01:29

Before the session, prosecutors agree that no words spoken in the session can ever be used against the witness unless he deliberately lies about something important -- something "material" as the lawyers would say.

In that case, all bets are off. No deal is forged, and the client may be prosecuted for whatever matter the prosecutors were initially investigating. He may also be charged with another serious crime: lying to federal law enforcement authorities.

"Queen for a Day" sessions are tense, often dangerous forums, even for an innocent person facing a wolf pack of determined, prosecutorial interrogators. If his lawyer terminates the session and advises his client to walk, all bets are off

To be clear, not all witnesses who seek an immunity deal or agree to a "Queen for a Day" proffer session are guilty of something. A completely innocent person with a particularly diligent lawyer may seek immunity just to be safe in a "highly politicized, witch-hunt environment," as Kelner observed.

On the other hand, good lawyers know that a client with real criminal liability is likely to get a better deal if he is the first to walk through the immunity door with a satchel of information that can help prosecutors make a case against others ... particularly highly placed others.

In the TV show, the "Queen for a Day" winner was the contestant who told the most tragic life story as judged by the audience applause meter. She was awarded a crown, a robe and often a washing machine or similar appliance.

In the justice system's modern version of the show, no crown is awarded, but on the other hand, you get to go home. The people you implicate may not. It remains to be seen if Flynn will be allowed to compete.