WASHINGTON, March 4 — In a rare rebuke of military investigators, the Defense Department inspector general has told the Army to open a criminal inquiry into the shooting death of Cpl. Pat Tillman, the former professional football player whose enlistment in the Army drew national attention, Pentagon officials said Saturday.
The new inquiry into the killing of Corporal Tillman, a member of the elite Rangers, will be conducted by the Army Criminal Investigation Command. The Army initially had said he died as a hero in a blaze of enemy fire in Afghanistan in 2004 before attributing his death to an accidental shooting by fellow Rangers.
The inquiry follows three other military investigations — two by his Army Ranger unit and one by its parent organization, the United States Army Special Operations Command — that the inspector general's office has now determined were deficient.
The earlier investigations found a series of crucial errors made by Corporal Tillman's fellow Rangers in the heat of combat, but found no criminal wrongdoing.
The new inquiry would be the first criminal investigation into Corporal Tillman's death, a move that military law experts said was unusual and significant.
"It obviously could lead to one of three things," said Eugene Fidell, who teaches military law at the Washington College of Law at American University. "Was there a negligent homicide? Was there a dereliction of duty? Was there a cover-up?"
Pentagon officials said no new evidence had prompted the inquiry and would not speculate about the outcome or timing. But the officials said that given the confusion on a battlefield, it would be highly unusual to pursue criminal charges against a soldier for the death of a comrade.
Col. Joseph Curtin, an Army spokesman, said that the scope of the new inquiry had yet to be defined but that investigators would look at whether the soldiers violated military law when they failed to identify their targets before opening fire on his position.
Corporal Tillman's parents, who were notified Friday of the investigation, have long complained about the findings and contradictions in thousands of pages of earlier investigations and have said there was evidence of a crime.
Patrick K. Tillman, Corporal Tillman's father, said Saturday that he remained distrustful of the military.
"You're assigning the same folks that have been asked several times to address this issue," Mr. Tillman, of San Jose, Calif., said in a telephone interview. "You're asking them to prosecute something when three times they have said there was nothing to prosecute? Do you really expect them to do it right?"
A Pentagon spokesman, Bryan Whitman, said that the inspector general in ordering another inquiry had not found evidence of a criminal offense, in Corporal Tillman's death or in the other investigations.
Rather, Mr. Whitman said, the inspector general concluded that the Army had failed to conduct a thorough enough investigation, including the possibility of criminal activity, immediately after Corporal Tillman's death on April 22, 2004.
Corporal Tillman's death first drew national notice because of who he was: a successful young N.F.L. safety who had walked away from a $3.6 million contract with the Arizona Cardinals to enlist, then qualified for the elite Rangers, with his brother after the terrorist attacks of 2001.
His death drew perhaps more attention than any other in the Afghanistan conflict, more so after it became clear that he had died not from enemy fire as he led his Ranger team up a hill, but from the fire of his own unit.
Earlier investigations found that for at least three weeks, as the Army allowed Corporal Tillman to be celebrated by the news media and mourned by his family as a war hero killed by the enemy, it actually knew of the more complicated circumstances of his death.
Corporal Tillman, 27, died beside a boulder along a craggy stretch of land in southeastern Afghanistan. His Ranger unit had been split into two parts, the first of a series of circumstances that led to confusion, miscommunication and fatal errors before his death, the Army's earlier investigations have shown.
At one point, one section of the unit reported coming under sudden attack and began returning volleys at what they said they believed was the enemy. After firing hundreds of rounds, the men in the convoy discovered that they had actually been shooting at men in the other half of their unit — a group they said they had believed was miles away, the earlier investigations showed.
An Afghan soldier fighting alongside the Rangers was killed, as was Corporal Tillman, who had tried desperately to alert his colleagues to his identity, the investigations showed. He had waved his arms frantically and called out, "Friendlies!" to alert the other Rangers, according to the statement of a Ranger who was near him.
Those who fired on Corporal Tillman described a hectic, confusing scene to investigators, and said they had made an unavoidable error in the blur of a firefight. They said they could not see him and fired in the direction of muzzle flashes that they believed to be the enemy.
Seven Army members faced administrative disciplinary action — though not criminal prosecution — after the shooting. They were cited by the military for failing to "provide adequate command of subordinate units," for dereliction of duty, and for failing to command and control the fire and movement of subordinates, Army documents show.
Corporal Tillman's family has long raised questions about the details of the investigations. His father has pointed to contradictions in descriptions by witnesses and investigators about the lighting at the time, the distances between those shooting and Corporal Tillman, and the communication between the groups. There have also been questions about the fate of much of the evidence, including his son's body armor and uniform, which were burned.
"We still don't know what happened," Mr. Tillman said.
Last year, the Defense Department inspector general's office opened a review into the case after the Tillman family criticized the earlier findings. Mr. Tillman said he was told on Friday that the inspector general's investigation would also continue.
Mr. Whitman, the Pentagon spokesman, said of the inspector general's decision to order the criminal investigation: "They've called a process foul on the Army for using the wrong investigative tools. That said, there's no reason to believe the outcome will be any different."
Mr. Whitman and Army officials cautioned, however, that it was too soon to tell what the new inquiry would turn up.
"The Army deeply regrets the loss of Corporal Patrick Tillman's life and the lives of all soldiers in this war," an Army spokesman, Paul Boyce, said Saturday. "We again extend our condolences to his family and are working to bring this matter to thorough resolution."