It was not clear why Muhammad, who faces the death penalty if convicted, decided to fire his lawyers, who will serve as standby counsel to come out of last year's sniper-shooting spree that killed 10 people in Washington, D.C., and its suburbs in Maryland and Virginia in three weeks and terrorized the nation.
Just last week, Muhammad told Judge LeRoy F. Millette Jr. that he was satisfied with his attorneys.
In his 20-minute opening statement, Muhammad said nothing about the shootings except to deny involvement.
"I know what happened. I know what didn't happen. They're basing what they said about me on a theory. If we monitor (the evidence) step by step, it will all show I had nothing to do with these crimes," he told the jury.
Muhammad, 42, is charged in the slaying of Dean Harold Meyers, a 53-year-old Vietnam veteran gunned down outside a northern Virginia gas station last October.
Fellow suspect Lee Boyd Malvo, 18, who goes on trial separately next month in another killing in Virginia, appeared in court briefly Monday to allow a prosecution witness to identify him.
The two were arrested last Oct. 24 in Maryland. Prosecutors have said the shootings were part of a plot to extort $10 million from the government.
Prosecutors say Malvo has made several statements to police and jail guards in which he confessed involvement in many of the attacks. But Muhammad barely spoke to investigators, and offered only terse, one-word answers to questions in many pretrial hearings.
Muhammad spoke at length Monday about the nature of truth, saying at one point, "Jesus said, `Ye shall know the truth."' He also said he hopes to be found innocent "by the grace of Allah."
"There's three truths. The truth, the whole truth and nothing but the truth. I always thought there was just one truth," he said. "The facts should help us identify what's a lie, what's not a lie."
Muhammad asked the jury to pay close attention to the facts because "my life and my son's life is on the line," apparently a reference to Malvo. The two are not related, but have referred to each other as father and son.
A bank employee, Linda Thompson, testified she saw Muhammad and Malvo outside her bank in Manassas near the shooting scene, shortly before Meyers was killed. Prosecutors brought in Malvo, in an orange jumpsuit, for the woman to identify.
Muhammad asked Thompson why she thought the two were suspicious.
"Was it because we was black that you remember us?" he asked. She denied that race was an issue.
Muhammad declined to cross-examine the victim's brother, Larry Meyers, who testified about Dean Meyers' life and identified his brother from a gruesome crime-scene photo.
An expert witness, Mark Spicer, a sergeant major in the British army with extensive expertise as a sniper, testified that a sniper's "main weapon is his ability to spread terror over a much larger force than himself." He said snipers work in two-man teams, and that it would be nearly impossible to be successful working alone.
Under cross-examination, Muhammad asked Spicer, "Have you ever seen me shoot anyone?" He asked whether potential sniper tools like walkie-talkies, earplugs, maps and a video recorder also could have benign uses, like keeping tabs on his son at a mall.
Spicer agreed that most of the items have benign uses, but prosecutor Paul Ebert later grabbed a Bushmaster rifle, apparently the same one authorities believe was used in the shootings, and asked sarcastically, "Have you ever seen anyone walking around in a mall carrying something like that?"
Assistant prosecutor James Willett told the jury he plans to link Muhammad and Malvo to most of the shootings. He explained the importance of a spotter's role in a shooting, which will be an important issue at trial.
Defense lawyers have argued that Malvo fired the shot that killed Meyers. Because of that, they argue that Virginia law prohibits imposing the death penalty against Muhammad on one of the two capital murder counts he faces.
CBS News legal analyst Andrew Cohen says the jurors are likely to be very curious to hear from Muhammad, at least initially. He gives low marks for Muhammad's opening day defense:
"Before too long, jurors will expect facts and logic and substance from him and if he cannot or will not deliver I think jurors quickly will become bored and tune him out. And if that happens, Muhammad absolutely will be convicted and probably sentenced to death.
"Muhammad may be doing this to exert more control over his fate. But the only way it may work out well for him is if he connects in some real, emotional way with jurors. And I just don't see that happening. I think it is far more likely that jurors will come to resent Muhammad for wasting their time, especially if he doesn't get to the point of what is critical to the case.
"Muhammad's start was not a great one. His opening statement raised more questions than it answered and I'm not sure he scores points by telling jurors that he has a family -- all of the sniper victims, remember, had families and it is much more likely that jurors will be sympathetic to those folks.
"I think Muhammad is likely to be frustrated by the limitations that the judge places on him as the trial progresses. He is simply not going to be able to raise the issues he wants to raise either through prosecution witnesses or his own. And he also is not going to be able to make another speech until closing arguments," Cohen concludes.