Not exactly the same, because Nick appears to have some sort of actual mental illness and Gigante was faking it for 30 years, but as an example of slick lawyering using NGRI, Gigante was able to avoid prison for decades.
All LE and all the other Mob bosses knew it was an act. So did all of NYC. He’d go outside in a ratty bathrobe, mumble nonsense, etcetera, while meanwhile he was one of the most powerful and brutal Mafia bosses.
It worked until it didn’t, but he avoided prison for 30 years.
Below is an excerpt from his Wikipedia page:
With the arrest and conviction of Gotti and various Gambino family members in 1992, Gigante was recognized as the most powerful crime boss in the United States. For about 30 years, Gigante
feigned insanity in an effort to throw law enforcement off his trail.
Dubbed "The Oddfather" and "The Enigma in the Bathrobe" by the media, Gigante often wandered the streets of Greenwich Village in his bathrobe and slippers, mumbling incoherently to himself. He was indicted on federal racketeering charges in 1990, but was determined to be mentally unfit to stand trial. In 1997, he was tried and convicted of
racketeering and
conspiracy, and sentenced to 12 years in prison. Facing
obstruction of justice charges in 2003, he pleaded guilty and admitted that his supposed insanity was an elaborate effort to avoid prosecution, as he was sentenced to an additional three years in prison. He died in the
United States Medical Center for Federal Prisoners on December 19, 2005.
en.wikipedia.org