Of course they can. In fact. This is the only verdict possible. The question should be can suspected Terrorists get a fair trial in a NYC Court? Still the answer is no. Judges are on a suspects payroll so the Defenses evidence will be suppressed, thrown out or completely banned from arguing there case. Ever want to see a Kangaroo Court put the Terror suspects on trial in the U.S. I doubt they will be able to arrest and extradite the 10 hijackers who are confirmed alive. Obviously the Government's list they suddenly had the day after 9-11 has the wrong suspects. Funny how they can identify them so quickly and didn't suspect them before 9-11. Even after the August 2001 Memo claiming Bin Laden plans to fly planes into the WTC. If I was water boarded 144 times I would admit to it also. There were no Terrorists on those planes the flight crew was inflatable and the destination was pre-programmed in the auto-pilot. How else did the planes fly at speeds exceeding the VRO by over 100 knots flawlessly?
No, 9/11 terror suspects might not be convicted by civilian courts, because there are too many loopholes and too many things left to chance in civilian courts. In civilian courts, things are often left to the opinion of the jury. The juries in New York are not representative of people all over the United States, so a jury would not be fair to Americans.
No, the NYC civilian courts cannot ensure conviction of the 9/11 terrorists, because the 9/11 terrorists declared war on the United States, and should not be tried by jury. Allowing a jury to try the combatants leaves room for public opinion and personal prejudices to influence appropriate outcomes. Trial by tribunal is the only way to assure a conviction.