HAMBURG, Germany -- The only Sept. 11, 2001, suspect ever convicted walked out of jail Wednesday smiling and laughing, freed less than 2 1/2 years into a 15-year sentence after judges ruled the evidence was too weak to hold him pending a retrial.

Mounir el Motassadeq, whose conviction on charges of aiding the Sept. 11, 2001, plotters was overturned last month, seemed euphoric as he left the Hamburg court building with two friends and his attorney. He said nothing but laughed as reporters peppered him with questions.

The 30-year-old Moroccan, who had been behind bars since his November 2001 arrest, headed home to his apartment in a Hamburg suburb to be reunited with his wife and two children.

Explaining their decision, the judges said evidence for the main charges against el Motassadeq -- more than 3,000 counts of accessory to murder -- was no longer "urgent" because they lack testimony from an al-Qaida suspect in U.S. custody. El Motassadeq was ordered to stay in Hamburg and report to police twice a week.

The accessory to murder charges remain in force, along with a charge of membership in a terrorist organization. But freeing el Motassadeq was a fresh blow to Sept. 11 prosecutions after the same court acquitted his friend and fellow Moroccan Abdelghani Mzoudi of identical charges in February.

The court's decision infuriated a spokesman for Americans whose relatives were killed in the Sept. 11, 2001, attacks. Stephen Push said he remains convinced of el Motassadeq's guilt.

"We don't want to see people who are involved in a conspiracy to kill our loved ones go free," said Push, a founder of the New York-based Families of Sept. 11 group. Push's wife was aboard the hijacked plane that crashed into the Pentagon.

"These people should be in prison," he said by telephone from Virginia.

In Washington, State Department deputy spokesman Adam Ereli expressed disappointment over el Motassadeq's release.

"We believe the evidence against him is strong and we believe he is a dangerous guy," Ereli said.

El Motassadeq has acknowledged training at an al-Qaida camp in Afghanistan and being close friends with Hamburg-based suicide hijackers Mohamed Atta, Marwan al-Shehhi and Ziad Jarrah. He has denied knowing of the plot to attack the United States.

He had been held in a red-brick Hamburg prison since being convicted in February 2003 of giving logistical help to the Hamburg al-Qaida cell.

An appeals court last month threw out el Motassadeq's conviction and ordered a retrial starting June 16. It said he was denied a fair trial because the United States would not grant his attorneys access to his friend Ramzi Binalshibh -- a Yemeni captured in Pakistan and now in American custody.

Binalshibh is believed to have been the Hamburg cell's main contact with Osama bin Laden's al-Qaida network, and defense lawyers say he might be able to testify that el Motassadeq was not involved in the plot.

Prosecutors allege el Motassadeq knew about the planned attacks on the Pentagon and the World Trade Center and helped cell members conceal their involvement while they lived and studied in Hamburg.

They say the former electrical engineering student used his power of attorney over al-Shehhi's bank account to pay rent, tuition and utility bills, allowing the plotters to keep up the appearance of studying in Germany. He also signed Atta's will.

El Motassadeq explained both as things he simply did for friends.

Defense attorney Josef Graessle-Muenscher predicted the retrial would fail unless the United States provides more evidence.

"I would like the Americans to really open all their books and give all the files and witnesses we need for there to be a chance for a fair trial," he said.

At a hearing Friday, new evidence emerged that could help El Motassadeq.

The court was presented with an intercepted 2003 telephone call in which suspected cell member Said Bahaji told his wife that he and others close to the hijackers knew nothing of the planned attacks.

Also presented was a 2002 letter from Bahaji to his mother in which he wrote "Mounir didn't know anything."

German authorities say Bahaji left Germany shortly before the Sept. 11 attacks and remains on the run.

If convicted only of the lesser charge of belonging to a terror organization, el Motassadeq would face a possible 10-year sentence.

Absence of testimony from Binalshibh also helped bring about Mzoudi's acquittal in February.

Mzoudi's case turned in his favor when the Hamburg court heard a statement from an unidentified source saying that only Binalshibh and the suicide hijackers knew of the Sept. 11 plot. The court said it believed the source was Binalshibh himself.