Federal law-enforcement agencies are referring fewer criminal investigations for prosecution, including white-collar crimes, long a mainstay of the FBI's crime-fighting mission.

A recent study by the Transactional Records Action Clearinghouse, a Syracuse University research center, found the FBI is instead focusing more on terrorism cases, especially after the Sept. 11, 2001, attacks.

The Secret Service, Internal Revenue Service and Postal Inspection Service, which also have long focused on white-collar crimes, also had big declines. White-collar crimes include fraud, identity theft, money laundering and environmental, health and safety violations.

At the Secret Service, for example, case referrals to prosecutors were down 67 percent from 1987 to 2007 when excluding immigration-related investigations.

The IRS had a 36 percent drop, while the Postal Inspection Service had a 45 percent decrease. FBI referrals for prosecution were down 51 percent.

Annual immigration-related cases, by contrast, increased more than four times during this 20-year period, from 9,883 in 1987 to 41,645 in 2007.

In addition to focusing more on terrorism cases, the FBI is working on more "white-collar crime cases that are more sophisticated" and thus take longer to investigate, said Laura Eimiller, an FBI spokeswoman in Los Angeles.

Rather than just going after an individual committing a crime, the agency is making a greater effort to look "at the whole organization and the masterminds behind a particular crime," Eimiller said.

The Syracuse study was based on 6.8 million Justice Department records obtained under the Freedom of Information Act.

In 2000, federal prosecutors filed 765 cases for organized crime. But in 2006, only 321 such cases were filed, a 58 percent drop.

There was also a decline in prosecutions for government corruption (down 10 percent) and narcotics and drug cases (down 18 percent).

Immigration-related prosecutions, however, increased by 215 percent over the same period and terrorism cases by 776 percent.

The study found that local law enforcement agencies are handling a greater share of white-collar cases.

Robert Myers, supervising attorney with the Ventura County District Attorney's Office, said he's noticed a marked increase in major fraud cases.

Some of the increase is because of the proliferation of computers and electronic gadgets that have created new areas of opportunity for criminals. "For example, we're seeing a lot more identity thefts," Myers said.

The real-estate boom also led to more predatory lending and fraud, he said.

Local prosecutors have struggled to keep up with the increased case load, Myers said.

Prosecutors have received some help, however, such as a trust fund created to help them prosecute real-estate fraud, he said.

Kevin R. Johnson, an associate dean at the UC Davis School of Law who has written extensively about immigration law and policy, said investigating and prosecuting immigration-related cases is often a lot easier than going after white-collar crime.

"Immigration-related convictions are fairly easy," Johnson said, and thus less of a risk for federal prosecutors.

Federal law-enforcement agencies, however, would be making much better use of their limited resources if they focused more on crimes where they can have a real impact, such as white-collar offenses, Johnson said.

The drop in white-collar investigations and prosecutions could spur more crimes and cause people to question the honesty and fairness of institutions.

"If people perceive the system to be unfair, they not only become disenchanted" but might also ask "why they should follow the rules when those in power aren't held accountable," Johnson said.