The trial has begun in the US of a man already imprisoned for his role in a 1995 bomb attack on an Oklahoma City building that killed 168 people.
If convicted, Nichols will faces death by lethal injection
Terry Nichols is serving a life sentence on charges relating to the deaths of eight officers in the attack.
He is now being tried for the murder of the bomb's numerous victims - a charge that could carry the death sentence.
Nichols' accomplice, white supremacist Timothy McVeigh, was executed in June 2001 for planting the bomb.
The first day of the new trial was spent selecting a jury - a process that is expected to last at least another fortnight.
Roughly 150 prospective jurors applied to sit on the trial at a courtroom in the town of McAlester, Oklahoma state.
Of these, the judge selected 42 individuals, dismissing the rest.
"The process is going to take some time," Judge Steven Taylor told the prospective jurors.
Nichols' defence team had tried to get the start of the trial postponed so that it could wait for an FBI review into its own investigation of the bomb.
Judge Taylor dismissed this request for the trial to be delayed earlier on Monday.
Although Nichols was at home when the bomb exploded, prosecutors believe he closely helped McVeigh plan the attack and his subsequent escape in a getaway car.
The prosecutors also want to ensure Nichols never successfully appeals against his conviction and gains his freedom.
However, lawyers for Nichols say they have uncovered a
wider conspiracy behind the bombing, for which Nichols is merely the scapegoat.