Urge prompt action. Wherever you are, you are under federal, state and local jurisdiction. The typical U.S. attorney's office would probably welcome a break in the tedium of frauds and stolen rugs. Similarly, state prosecutors are quite interested in such cases. Some local law enforcement agencies, including Montgomery County, Md., have detailed one or two officers to investigate computer crime.
Law enforcement has big weapons.
With enough evidence, the government can seek a judicial search warrant permitting the search and seizure of the suspect's computer. This judicial probable-cause standard is actually less than what is needed by a private party to win civil lawsuit. The beauty of the search warrant is its unexpectedness. Arrogant thieves often leave the most damning evidence right on the hard drives of their own PCs. The law also makes it a criminal act for an individual or organization to destroy or alter such information.