A judge declared a mistrial Tuesday in the case of two Mexican immigrants charged with killing three of their young relatives -- one of the city's grisliest and most puzzling crimes -- after jurors said on their 10th full day of deliberations that they were hopelessly deadlocked.

The decision means that, for now, no one has been found responsible for nearly decapitating the children, ages 8, 9 and 10, inside a cramped northwest Baltimore apartment in May 2004.

Immediately after Judge Thomas Ward declared the jury hung, prosecutor Sharon R. Holback pledged to retry what she called a "very complicated and difficult case." The trial, which included five weeks of testimony, was one of the longest in recent memory in Baltimore Circuit Court.

Holback said, "On behalf of the children that suffered and died, we're going to get some rest, and then we're going to come back and we're going to try this case again, because these children and the community at large deserve justice and closure in this case."

The defendants, Adan Espinoza Canela, 18, and his uncle Policarpio Espinoza Perez, 23, did not visibly react as Ward questioned the jury, concluded that further deliberations would be of no use and declared a mistrial. That outcome had seemed increasingly likely since the middle of last week, when jurors said they were deadlocked and Ward instructed them to continue their discussions.

Afterward, Espinoza Canela and Espinoza Perez were led from the courtroom in handcuffs and leg irons. They are being held without bond, as they have been since they were charged with first-degree murder and other offenses hours after the slayings.

The jury of seven women and five men was deeply divided from the start, two of the jurors said yesterday, and it made little progress as deliberations stretched into a third week. The jurors said that throughout their discussions, the panel was split on Espinoza Canela's guilt. It tilted in favor of convicting Espinoza Perez, 8 to 4, by the middle of last week, they said.

The jury was unusually inquisitive, seizing on Ward's invitation to put questions to the court, even to witnesses, throughout the trial. Jurors submitted more than 70 notes, some of which provided a glimpse into the dynamics of the panel, if not the views of its members. One note read: "Can it be addressed regarding jurors chewing and popping gum in the other jurors ears. Please."

Prosecutors contended during the trial that blood and DNA evidence linked the men to the slayings of Ricardo Espinoza, 9, his sister Lucero Espinoza, 8, and Alexis Espejo Quezada, 10, another relative. The jury also learned that Espinoza Perez told police he was outside the apartment at the time of the killings.

Yet the prosecution could offer no clear motive for the crimes, contending instead that the children were slain because of a "family secret" that their surviving relatives refuse even now to divulge. Those relatives, including the parents of the children, testified that they believed the defendants were not guilty.

Although juror Michael Johnson said the absence of a motive was a "big mystery," the other two jurors said it was not a major factor during deliberations that hinged more on physical evidence. Juror Keith Brown said the close genetic ties among the family members made conclusive DNA matching -- which was among the evidence that prosecutors had said was central to their case -- difficult at best.

"The DNA evidence brought up a lot of problems for us," Brown said.

Brown said a majority of the jury believed that more than two people were involved in the slayings. "We did feel that there was somewhat of a conspiracy throughout the whole family," he said.

Brown and the other juror, who spoke on condition of anonymity, said the panel tilted toward convicting Espinoza Perez because the statement he gave police put him at the scene. Brown, who favored convicting both men, questioned why "Adan's name was not brought up in that statement at all."

What the jury did not hear, however, was that Espinoza Perez told police that he waited in the car while Espinoza Canela entered the apartment where the children were and climbed out a rear window about half an hour later. That portion of the statement was not admissible in the joint trial because defendants have a right to question any witnesses against them, and Espinoza Canela could not be forced to testify at his own trial.

Espinoza Perez's attorney, Timothy M. Dixon, said his client was relieved by the outcome, even though he faces another trial. Dixon suggested during the trial that police, who were under extreme pressure to solve the high-profile crime, planted "manufactured" evidence to frame his client. Espinoza Canela's attorney, James Rhodes, said his client was disheartened by the mistrial and confused about what it might mean for him.

Later in the day, at a conference room in a law office, both defense attorneys appeared with the parents of Lucero and Ricardo, along with a family spokesman, Jorge "George" Zapada. As the parents sat silently, eyes downcast, the spokesman dismissed the prosecutors' suggestion that a family secret might explain the slayings.

"This is a lie," Zapada said.

Staff writer Ray Rivera contributed to this report.

Juror Michael Johnson called the absence of a motive in the slayings "a big mystery."