OKLAHOMA CITY ? Oklahoma City bombing conspirator Terry Nichols’ defense in his federal case cost U.S. taxpayers almost $6.3 million, records show.

The amount was concealed until the completion of Nichols’ state case. U.S. District Judge Richard Matsch and the 10th U.S. Circuit Court of Appeals released the figures after media requests, The Oklahoman reported.

Besides the trial costs, taxpayers shelled out $107,428 for Nichols’ appeals of his 1997 conviction on conspiracy and involuntary manslaughter for the deaths of eight federal agents in the April 19, 1995, bombing of the Alfred P. Murrah Federal Building.

The blast killed 168 people and injured more than 500.

Nichols, who is serving life sentences without the possibility of parole, was allowed free legal help because he couldn’t afford it.

“The system of public funding for legal representation, particularly in capital cases, is an important guarantee of constitutional rights,” said his lead federal attorney, Michael Tigar. “All lawyers ought to support its wise use.”

Tigar was paid $125 an hour, much less than his usual fee. He said his legal team tried to economize but spent a lot of money on trying “to smoke out” information from the federal government.

In comparison, the cost to defend Nichols, 50, in his state case, in which he was convicted of 161 counts of first-degree murder and sentenced to life without parole, was about $4.12 million.

Most of that money came from the Oklahoma County court fund, a collection of civil case fees, criminal fines, bond forfeitures and other money paid to the court clerk.

Taxpayers spent $15 million on bomber Timothy McVeigh’s defense at trial and his appeals.

In all, the federal government reported spending more than $82.5 million to investigate the bombing and prosecute the federal cases.

Authorities acknowledge that Nichols was at his home in Herrington, Kan., on the day the bomb went off. But they allege Nichols worked with McVeigh to prepare the 4,000-pound bomb and helped McVeigh pack it inside a Ryder truck.