WASHINGTON — The number of Americans being secretly wiretapped or having their financial and other records reviewed by the government has continued to increase as officials aggressively use powers approved after the Sept. 11, 2001, attacks.
But the number of terrorism prosecutions ending up in court — one measure of the effectiveness of such sleuthing — has continued to decline, in some cases precipitously.
The trends, visible in new government data and a private analysis of Justice Department records, are worrisome to civil liberties groups and some legal scholars. They say it is further evidence that the government has compromised the privacy rights of ordinary citizens without much to show for it.
The emphasis on spy programs is also starting to give pause to some members of Congress who fear the government is investing too much in antiterror programs at the expense of traditional crime-fighting.
Other lawmakers are raising questions about how well the FBI is performing its counterterrorism mission.
The Senate Intelligence Committee concluded last week that the bureau was far behind in making internal changes needed to keep the nation safe from terrorist threats.
Lawmakers urged the FBI to set specific benchmarks to measure its progress and make more regular reports to Congress.
These concerns come as the Bush administration has been seeking to expand its ability to gather intelligence without prior court approval. It has asked Congress for amendments to the 1978 Foreign Intelligence Surveillance Act to make it clear that eavesdropping on foreign telecommunications signals routed through the United States does not require a warrant.
Law enforcement officials say the additional surveillance powers have been critically important in ways the public does not always see.
Threats can be mitigated, they say, by deporting suspicious individuals or letting them know that authorities are watching them.
"The fact that the prosecutions are down doesn't mean that the utility of these investigations is down. It suggests that these investigations may be leading to other forms of prevention and protection," said Thomas Newcomb, a former Bush White House national security adviser. He said there are a half a dozen actions outside the criminal courts the government can take to snuff out potential threats, including using diplomatic or military channels.
While legal experts say they would not necessarily expect the number of prosecutions to rise along with the stepped-up surveillance, there are few other good ways to measure how well the government is progressing in keeping the country safe.
"How does one measure the success? The short answer is we aren't in a great position to know," said Daniel Richman, a former federal prosecutor. With prosecutions declining, he said, the public is left with imperfect and possibly even misleading ways to gauge progress in the Bush administration's war on terrorism — such as the number of secret warrants the government issues or the number of agents it assigns to terrorism cases.