An agency with approximately 4,000 employees, 2,000 criminal investigators, an armed uniformed division with 1,000 personnel, forensic laboratories and a robust communications system, and with 1,000 technical and administrative support personnel, the USPIS is a major federal law enforcement agency that leads and assists in numerous joint federal and state investigations.
In 1801, the title of "surveyor" was changed to Special Agent. Thus, the Service's origins—in part—predate the Declaration of Independence, and therefore the United States itself. As Franklin was Postmaster under the Continental Congress and was George Washington's first Postmaster, his system continued.
In 1830, the Special Agents were organized into the Office of Instructions and Mail Depredations. The Postal Inspection Service was the first federal law enforcement agency to use the title Special Agent for its officers. Congress changed this title to Inspector in 1880.
For some time, one of their primary duties was the enforcement of obscenity prohibitions under the Comstock Act.
The OIG primarily took over the Postal Inspection Service's audit function, as well as fraud (against the USPS) waste and abuse.
The USPIS is primarily an investigative agency comprising of plain-clothes federal criminal investigators entitled "Postal Inspectors" whose primary mission is "to protect the U.S. Postal Service, its employees and its customers from criminal attack, and protect the nation's mail system from criminal misuse". It has responsibility for over 700,000 Postal Service employees and billions of pieces of mail transported through air, land, rail and sea world wide a year.
Since the September 11, 2001 attacks, the USPIS has also investigated several cases where ricin, anthrax and other toxic substances were sent through the mail. Although USPIS has a wide jurisdiction, USPIS investigations can be categorized into these six types of investigative teams and functions:
1) Fraud: These types of investigation involve crimes that use the mails to facilitate fraud against consumers, business and government. Federal statutes that surround these types of investigations include, mail fraud, and other criminal statues when they are tied to the mails such as bank fraud, identity theft, credit card fraud, wire fraud, and Internet/computer fraud. Mail fraud is a statute that is used in prosecuting many white collar crimes, this would include, Ponzi schemes, 419 frauds, and other white collar crimes where the mail was used to facilitate the fraud.
2) External Crime & Violent Crime Teams: The External Crimes Function of USPIS is a function that investigates any theft of US mail by non employees, assaults of postal employees and or theft and robberies of postal property. This function also investigates robberies of postal facilities and personnel, burglaries of postal facilities, and assaults and murders against postal personnel. This investigative function focuses on ensuring that the sanctity and trust in the U.S. Mail system is maintained.
3) Prohibited Mailing Investigations: Prohibited mailing investigations are USPIS investigations that focus on the prohibited mailing of contraband including: narcotics, precursors and proceeds; child pornography and other sexually prohibited materials; and hazardous materials to include, mail bombs, nuclear biological and chemical weapons. The laundering of narcotics and other criminal proceeds through the use of Postal Money Orders are sometimes categorized under this investigative function.
4) Aviation and Homeland Security: USPIS investigations also include the securing and protecting of transportation of US Mail and any risk that might compromise the security of the homeland because of these mails. Security Audits are conducted by these teams to ensure that postal service maintains facilities secure from not only theft and robberies but also natural and manmade disasters.
5) Revenue Investigations: USPIS investigates cases where fraudulent practices are conducted by business and consumers that mail items without proper or counterfeit postage and indicia or crimes that defraud the USPS of revenue.
6) International Investigations and Global Security: This investigative function ensures that international mail is secured and any international business decisions and campaigns remains safe, and secure. USPIS maintains investigators in the US and in posts around the world for protection, liaison, and intelligence.
In addition to plain-clothes inspectors, there is the uniformed Postal Security Force whose security police officers protect major postal facilities, escort high-value mail shipments, and perform other protective functions.
The Postal Inspection Service operates one main forensic crime laboratory that is staffed by forensic scientists whose expertise includes the examination of physical and digital evidence. The crime laboratory also has several satellite offices across the country whose primary mission is computer forensics. The Postal Inspection Service's Technical Services Division (TSD) provides investigative support through the use of new technology and the operations of two national communication centers known as the National Law Enforcement Control Centers or the "NLECC". [In 2003 Immigration and Customs Enforcement renamed their national communication center, previously known as "Sector" to the "National Law Enforcement COMMUNICATIONS Center" also known as "NLECC", USPIS NLECC and ICE NLECC are two independent federal law enforcement radio communications centers but coincidentally share the same acronym and an almost identical name).