Vincent Gigante, considered the most powerful Mafia boss in America but perhaps best known for walking through his Greenwich Village neighborhood in a bathrobe and pajamas, was declared mentally competent Wednesday to stand trial on murder and racketeering charges by a judge who called his odd behavior an “elaborate deception.”

Judge Eugene H. Nickerson of U.S. District Court in Brooklyn found that the reputed head of the Genovese crime family “has feigned illness for over 20 years” in an attempt to skirt prosecution.

Gigante’s organization is considered the wealthiest Mafia group in the nation, until recently having major influence on lucrative industries and operations like garbage hauling, the docks in New Jersey, the Fulton Fish Market and the Jacob K. Javits Convention Center.

But in recent years, the family’s purported influence in these areas has come under a withering attack by law enforcement agencies and New York City officials. Wednesday’s ruling was just the latest blow.

In his ruling, Nickerson said Gigante had feigned mental illness “to hide his criminal activities and to evade prosecution,” in this case on charges that he ordered the murders of six mob figures, participated in the killings of two more and conspired unsuccessfully to commit still more murders - including that of his onetime archrival, John Gotti.

The judge’s decision culminated six years of courtroom battling over Gigante’s mental condition, and prosecutors said the finding could not be appealed before a trial is held.