As news breaks that Chelsea bomber Ahmad Khan Rahami’s father contacted the FBI two years ago to report that he feared his son was a “terrorist” (as did the father of the “underwear bomber” to the CIA), a slight discrepancy has surfaced between reports published by The New York Times and The Guardian. While the Times reports that the FBI conducted an “assessment” of Rahami after his father’s warning, The Guardian uses the phrase “preliminary investigation.”

Although The Guardian quotes the FBI as stating, “In August 2014, the FBI initiated an assessment of Ahmad Rahami” (emphasis added), the paper uses the term “preliminary investigation.”

The FBI conducted a preliminary investigation into Rahami after his father contacted them following a 2014 stabbing to express concerns that his son was a terrorist.

…The FBI did not clarify if it interviewed Rahami, who was captured in a shootout with police yesterday, in 2014, but confirmed it conducted a preliminary investigation.

The Times, however, consistently uses the word “assessment” throughout its story:

The information was passed to the Joint Terrorism Task Force led by F.B.I. in Newark. Officers opened what is known as an assessment, the most basic of F.B.I. investigations, and interviewed the father multiple times.

…The assessment of Mr. Rahami illustrates the challenges the F.B.I. faces as it solicits information from the public about people who might pose a threat and then must sort through what is credible, while balancing the need to protect the country without overstepping its authority.

…Like Mr. Rahami, one of the Boston bombers, Tamerlan Tsarnaev, was the subject of an assessment in 2011.

…While the federal assessment of Mr. Rahami was closed weeks after it began…

While this discrepancy between The New York Times and The Guardian may appear to the average reader as simply a difference in word choice, there’s actually a legal or operational difference between an FBI “assessment” and a “preliminary investigation.” According to the Times:

Depending on the intensity and urgency of an inquiry, there are three types of investigations the F.B.I. can undertake with varying levels of intrusive techniques.

The first is an assessment, in which agents use basic techniques like conducting interviews, talking to confidential informers, using physical surveillance and checking databases and public records.

Next come preliminary and full investigations, which can be initiated if agents believe a federal crime has been committed or there is a threat to national security. Those investigations can involve polygraphs, undercover agents and mail searches.

Both assessments and preliminary inquiries have time limits.

A full investigation has no such time limits, but does eventually require review and employs powerful electronic surveillance tools, requiring the approval of a court warrant. Among other things, it allows for the secret interception of international communications.

The Brennan Center for Justice at New York University School of Law, a law and policy institute that closely monitors the FBI’s tactics, adds a fourth category:

According to the FBI’s own Domestic Investigations and Operations Guide (DIOG), assessments and preliminary investigations are indeed separate entities. The DIOG defines yet another category, “enterprise investigation,” which “may only be opened and operated as a Full Investigation and is subject to the same requirements that apply to a Full Investigation… although there are addition approval requirements that affect Enterprise Investigations.” An enterprise investigation can only be used on “the most serious criminal or national security threats.” Its purpose is to “examine the structure, scope, and nature of the group or organization.”

Unless The Guardian knows something I don’t, it’s likely that it simply didn’t consider the real differences between “assessment” and “preliminary investigation.” The distinction seems rather harmless, but nonetheless important to point out.