Una James, 38, was subpoenaed by prosecutors to testify in Muhammad's trial in Virginia. She was scheduled to fly from her native Jamaica on Sunday, but refused at the last minute, saying she hadn't received assurances she could see her son, suspected of murder.
"Why is it that America says it stands for family first?," James told CVM television station in a broadcast aired Monday. "If that was an American child would he be without his mother by his side? Is that justice?"
James, who was deported to Jamaica in December 2002, said she doesn't have a lawyer and expressed concern about what might happen to her if she traveled to the United States without legal representation.
James added that she didn't see the point in returning to Jamaica after testifying in Muhammad's trial only to be summoned again for her son's, which begins Nov. 10.
It was unclear when James was subpoenaed or if a future trip is being planned. Virginia prosecutors did not return calls seeking comment.
U.S. Consulate officials this weekend denied James a visa to attend Muhammad's trial, but Virginia authorities and the U.S. Homeland Security Department (search) arranged for her transportation with an escort, U.S. Embassy spokeswoman Orna Blum said.
She later met inside with waiting U.S. officials for about 10 minutes before leaving the airport in a taxi without further explanation.
When reached on her cell phone Monday, James refused to comment, saying she wasn't speaking with the U.S. media.
In a June interview with Jamaican television, James lashed out at U.S. authorities, saying she warned them that Muhammad was a bad influence on her son prior to the shootings. U.S. authorities have disputed her claim.
Malvo, 18, and Muhammad, 42, allegedly took part in 20 shootings that killed 13 people in Virginia, Maryland, Georgia, Alabama, Louisiana and Washington, D.C. last year.
Prosecutors have said the three-week shooting spree was part of scheme to extort $10 million from the government. Both could face the death penalty if convicted.
In 1998, James and Malvo moved from Jamaica to Antigua, where they met Muhammad. Investigators believe she bought identification papers from Muhammad and entered the United States in late 2000 while her son stayed behind with Muhammad.
Malvo came to the United States bearing a false passport that identified him as Muhammad's son, according to Antiguan officials.
He joined his mother in Fort Myers, Fla., but ran away in October 2001 to join Muhammad in Bellingham, Wash., where they lived at a homeless shelter as father and son.
In September, James said she asked Bellingham police to help her get her son back. During the investigation, police said Malvo's comments indicated he and his mother were in the country illegally and officers summoned the Border Patrol, which arrested the mother and son and then released them on $1,500 bail.