Considerable hackles were raised last week by a critical report from the investigatory arm of the Senate Committee on Homeland Security and Governmental Affairs.

It focused on the Department of Homeland Security’s beloved “fusion centers” — clusters of state and local law enforcement people set up to collect intelligence on terrorist and other criminal activity in their area and then to send reports on their findings to DHS for evaluation.

Amazingly, after concluding — mildly but pointedly — that the utility of the terrorism-related reporting from the fusion centers has been “questionable,” the committee recommends that even more money should be spent on them. Local intelligence reporting efforts, it proclaims, should be reformed to eliminate duplication, the training and numbers of intelligence reporters should be improved, and better efforts to evaluate their output should be put into place.

Never once does the report consider that the reason intelligence reporting on the terrorists lurking in our midst is so limited in quantity and so abysmal in overall quality is that there is virtually nothing to report. Absence of evidence, it implies, cannot possibly be evidence of absence. We just have to work harder to find what surely must be out there.

DHS Secretary Janet Napolitano has called the fusion centers “one of the centerpieces of our counterterrorism strategy,” and DHS’s top intelligence official deems them “a vital tool for strengthening homeland security.”

No one seems to know how much these centerpieces, or vital tools, have cost. DHS estimates it has awarded somewhere between $289 million and $1.4 billion for fusion centers since 2003 — an uncertainty gap of over a billion dollars that is impressive even by Washington standards.

Moreover, it is not even clear how many fusion centers exist. DHS claims there are 72, but at least four of these were “not functional at a level to receive a visit,” including one which “was not operational” at all. One official helpfully suggested to the committee staff that some may operate as “virtual fusion centers.”

To evaluate the output from the centers — whether real or virtual — investigators shuffled through fusion center intelligence reports submitted to DHS over a 13-month period in 2009 and 2010. There were 610 of these from 31 states — centers in the other 19 submitted none at all — and more than half came from just two states: Texas and California.

Of the 574 unclassified reports filed, 188 were “cancelled” by DHS reviewers, generally because they contained “nothing of value” or simply failed to be devoid of “any actual intelligence.” While the overall cancellation rate for the reports was around 30 percent, nearly half of those dealing with terrorism were rejected out of hand.

That didn’t leave many. Of the 386 reports accepted, most relayed information from arrests or encounters relating to drug trafficking and alien smuggling. Only 94 — considerably less than two a week — related “in some way” to potential terrorist activity.

Moreover, more than a quarter of these 94 reports simply duplicated information already known to the FBI, and “some were based on information drawn from publicly available websites or dated public reports.” One, in fact, cheerfully relayed information from a Department of Justice press release that had been published months earlier.

More importantly, says the report, DHS has “struggled” to identify a clear example in which a fusion center provided intelligence that helped disrupt a terrorist plot. And, when investigators looked at the four “success stories” touted by DHS, they were “unable to confirm” that the fusion centers’ contributions were “as significant as DHS portrayed them; were unique to the intelligence and analytical work expected of fusion centers; or would not have occurred absent a fusion center.”

But things are considerably more problematic than that.

The report insists that, whatever the investigatory irrelevance of fusion centers, local and federal law enforcement have nonetheless “thwarted dozens of terrorist attacks on U.S. soil and against U.S. interests in the past decade.”

However, few of these cases ever reached the point — or were every likely to reach the point — where they could reasonably be considered to be “attacks,” and a great many were “thwarted” only because law enforcement had substantially invented them.

I’ve edited a web book containing a collection of studies of the 50 cases of Islamist extremist terrorism that have come to light since 9/11, whether based in the United States or abroad, in which the United States was, or apparently was, targeted. These make up (or generate) the chief terrorism fear for Americans.

In general, this set of case studies supports the conclusions of the committee report about the irrelevance of fusion centers. A similar conclusion can be derived from other related analyses of domestic terrorism.

Actually, however, it is not clear that any of the billions of dollars added to counterterrorism policing since 9/11 has been all that necessary. Michael Sheehan, New York’s deputy director for counterterrorism, has argued, “The most important work in protecting our country since 9/11 has been accomplished with the capacity that was in place when the event happened, not with any of the new capability bought since 9/11. I truly believe that those huge budget increases have not significantly contributed to our post‑9/​11 security.…The big wins had little to do with the new programs.”

Sheehan’s observation may be a bit excessive. It is not clear, however, that dealing with the vast majority of the terrorist plots and cases over the last decade has required expensive new technologies or dot-connecting “synergies” among policing agencies. For the most part, the potential perpetrators, in the words of the case study authors, were incompetent, ineffective, unintelligent, idiotic, ignorant, inadequate, unorganized, misguided, muddled, amateurish, dopey, unrealistic, moronic, irrational, and foolish. As such, they generally were fully susceptible to being uncovered by standard policing methods.

Although some of the plotters did harbor visions of toppling skyscrapers, destroying airports, setting off dirty bombs, or bringing down the Brooklyn Bridge, all such ventures were nothing more than wild fantasies, far beyond the would-be terrorists’ capacities. None has ever been able to detonate even the simplest of bombs (nor, except for the Underground bombings in London in 2005, have any of their counterparts in the United Kingdom). In fact, in most cases it seems likely that, despite the often childish fulminations of the participants, the plotters would never have fomented any violence at all. Indeed, in quite a few cases, they were “thwarted” even as they were in the process of abandoning their plot.

Moreover, in fully half of the cases, the agile activities of undercover police operatives were vital to the fabrication and particularly to the development of any plot by their gullible associates. As the judge in one terrorism trial concluded, “I believe beyond a shadow of a doubt that there would have been no crime here except the government instigated it, planned it and brought it to fruition.”

Exaggerations and distortions of the threat presented by terrorism have inspired a determined and expensive effort to ferret out, and even to create, the nearly nonexistent. The FBI, for example, occupies itself by questing after 2,000 “threats” a day, an exercise some in the agency have dubbed “ghost chasing.”

The committee has documented how useless fusion centers, one much-vaunted expenditure of energy and funds in the counterterrorism enterprise, have turned out to be. Yet, it seems unwilling to recognize that its own results indicate that the effort, and by extension much of the costly and massive campaign of which it is a centerpiece, is a highly questionable undertaking.

Despite its admirable and impressively researched efforts to critique one element in the quest to police domestic terrorism, the committee’s investigation may serve more nearly to perpetuate the process than to stimulate a fundamental and long-overdue re-evaluation of it.