Testimony ended Friday at the state murder trial of Oklahoma City bombing (search) conspirator Terry Nichols as prosecutors tried to refute defense theories that other accomplices helped plan the attack.

Prosecutors questioned 13 witnesses over two days of rebuttals that hammered key elements of Nichols' defense, including suggestions that executed bomber Timothy McVeigh (search) received substantial help in the bombing that killed 168 people.

Judge Steven Taylor excused the 12-member jury until Monday afternoon, when closing arguments are scheduled.

Taylor also denied Nichols' request for jurors to consider less serious charges when they deliberate. Jurors will now be limited to two possible verdicts in the case: guilty of first-degree murder or innocent.

"That was a huge victory for us," said Darlene Welch, whose 4-year-old niece, Ashley Megan Eckles, died in the bombing.

"It's all or nothing," Welch said.

Nichols had wanted the jury consider verdicts on lesser charges of second-degree murder or second-degree manslaughter.

Among the final witnesses was Tom Kessinger, a former body-shop mechanic in Junction City, Kan., who provided descriptions used by an FBI artist to develop sketches of two suspects who rented the Ryder truck that delivered the bomb.

One of the sketches closely resembled McVeigh, who was convicted on federal murder charges for the April 19, 1995, attack and executed in 2001.

The other sketch depicted a heavy man with brown eyes and hair whom Kessinger and other witnesses said was with McVeigh at the leasing agency. He said the man wore a black T-shirt, a baseball cap with white and blue zigzag patterns and had a tattoo on his left arm.

Authorities later concluded that the man, dubbed John Doe No. 2, was actually an innocent Army private from nearby Fort Riley, Todd Bunting, who was in the leasing agency on April 18, 1995, a day after McVeigh leased the truck.

Kessinger testified that he made a mistake in his description of John Doe No. 2, but he still believes McVeigh was accompanied by a second person.

"I didn't get to see much of John Doe No. 2, except for a side shot," Kessinger said.

Nichols, 49, is serving a life prison sentence after a federal jury convicted him in 1997 of conspiracy and the involuntary manslaughter of eight federal law enforcement agents in the bombing of the Alfred P. Murrah Federal Building (search).

In Oklahoma, Nichols is charged with 161 counts of first-degree murder for the deaths of the other 160 victims and one victim's fetus. Prosecutors are seeking the death penalty.