Did Army security or intelligence officials miss potential warning signs in the behavior of accused Fort Hood shooter Maj. Nidal Hasan? One issue that is likely to be examined by the inquiries into Hasan’s shooting spree is the effectiveness of Army security-clearance procedures. According to Wayne Hall, a spokesman at Army headquarters at the Pentagon, everyone who receives a commission as a U.S. Army officer has to undergo a security investigation, which qualifies him or her, at a minimum, to handle information classified “secret.” While Hall said he could offer no specific information on the status of security clearances held by Hasan, he said standard practice is that officers normally have to receive their secret clearance before they are formally commissioned, and that sometimes commissions are held up pending the successful conclusion of the security check. Hall said that these rules apply to all Army officers, and indicated he had no reason to believe that Maj. Hasan was an exception.

Army officers who are on active duty are supposed to have their security clearances reviewed and updated every five years if they have a top-secret clearance and every 15 years if they have only a secret clearance. Hasan’s official military record shows that he was first commissioned in June 1997, meaning that if his clearance is top secret, he should have been reinvestigated twice, most recently in 2007, but that if his clearance is only secret, he's not due for an update until 2012. When it comes to civilian Pentagon employees, security-clearance updates have been known to fall behind schedule—sometimes years behind. But when it comes to military officers on active duty, the service tries to stick to the rules to ensure the reliability of troops if they are sent into the field.

Two national-security officials, who asked for anonymity when discussing sensitive information, said that the standard procedure for vetting people for secret security clearances usually involves what is known as a National Agency Check, or NAC (a copy of the basic NAC rulebook can be read here). The most perfunctory NAC is a review of federal agency records, including FBI fingerprint records, and, in the case of someone who has lived abroad or has relatives abroad, the records of intelligence agencies like the CIA.

Extended NACs, which the officials indicated are more likely for would-be military officers, would include checks of local and state police records in jurisdictions where the subject lived, as well as credit-bureau and financial-record checks. In the event that some kind of “derogatory” information turns up during these checks, one of the officials said, field investigators are likely to be sent out to conduct interviews, and the procedure could also include an interview with the security-clearance applicant. If an applicant is required to have a clearance for top-secret information or even more rarefied clearances (like a Q clearance for nuclear-weapons information or an SI/TK clearance for spy-satellite data), then investigators are supposed to conduct a full-field background check involving extensive interviews with references, former employers, acquaintances, and even neighbors of people under investigation. Employees of certain intelligence agencies, including the CIA and intelligence czar’s office, also have to undergo polygraph examinations before being granted final clearance.

At this point there is no reason to believe that Hasan had anything higher than the standard secret clearance required by all officers at his level—though nobody has ruled out the possibility that his clearance could have been higher. But the extent to which the Army checked him out—and kept watch over him as he earned his psychiatry degree and rose through the ranks—will almost certainly come under scrutiny as investigations into his background and the motives to his shooting spree continue.

Clarification: Following additional inquiries from NEWSWEEK, the Army informed us that its rules for updating security clearances have recently changed and that the information the Pentagon originally gave us on this subject was wrong. The new rules are that top-secret clearances are renewed every five years and secret clearances are renewed every 15 years, although additional investigations can be conducted earlier if warranted.