The 2nd U.S. Circuit Court of Appeals in New York upheld the conviction of Adis Medunjanin, who was sentenced to life in prison in 2012 after a jury found him guilty on charges that included conspiracy to use weapons of mass destruction and conspiracy to commit an act of terrorism.
Lawyers for Medunjanin, 30, argued that a trial judge in Brooklyn, New York, erred in rejecting his request to suppress incriminating statements he made to law enforcement after his 2010 arrest.
They said the statements, which were made without an attorney present, violated his right to counsel and were a product of government coercion.
But a three-judge 2nd Circuit panel said there was "no sound basis" to conclude that the government's conduct violated Medunjanin's rights.
Robert Gottlieb, a lawyer for Medunjanin, in an email said he would seek review by the U.S. Supreme Court.
"The constitutional right to an attorney applies to everyone, no matter who he is or what the charges might be," he said.
A spokeswoman for Brooklyn U.S. Attorney Loretta Lynch did not respond to a request for comment.
U.S. Attorney General Eric Holder has said the case involved "one of the most serious terrorist threats" to the United States since the Sept. 11, 2001, attacks on New York and Washington.
Prosecutors said Medunjanin and his co-plotters agreed in 2008 to travel to Pakistan, intending to fight with the Taliban against U.S. forces in Afghanistan.
They were instead persuaded to receive training from al Qaeda and return to New York for a planned attack on one of the world's busiest subway systems, prosecutors said.
Medunjanin's accused co-conspirator Najibullah Zazi was arrested in September 2009, just days before Medunjanin and a third member of the plot, Zarein Ahmedzay, planned to carry out the bomb plot, prosecutors said.
Ahmedzay and Zazi, who were high school friends of Medunjanin, pleaded guilty to planning the attacks with him and cooperated with the government. A jury convicted Medunjanin in 2012.
Medunjanin's appeal centered in large part on events leading up to his arrest in January 2010, after agents from the Federal Bureau of Investigation executed a search warrant on his home for his U.S. and Bosnian passports.
Upset about the search, Medunjanin left his home that night and later crashed his car while driving at high speed.
At a hospital, law enforcement questioned Medunjanin, who signed a form waiving his so-called Miranda rights to remain silent and have a lawyer present.
During questioning, Medunjanin admitted he traveled to Pakistan with Zazi and Ahmedzay and said he had hoped the car crash would cause an explosion killing other people.
Medunjanin's lawyers called the waiver of his Miranda rights a "product of intimidation, coercion and deception."
U.S. Circuit Judge Amalya Kearse disagreed, saying the "record provides no basis for overturning the district court's conclusion that Medunjanin's will was not overborne."