The U.S. Postal Inspection Service maintains a state-of-the-art National Forensic Laboratory in Dulles, VA, comprising highly trained forensic scientists and technical specialists who play a key role in identifying, apprehending, prosecuting, and convicting individuals responsible for postal-related criminal offenses. Its mission is to provide scientific and technical expertise to the criminal and security investigations of the U.S. Postal Inspection Service. Laboratory services are divided into the units described below.



Questioned Documents Unit
The Questioned Document Unit provides technical assistance to Postal Inspectors who are investigating suspected violations of postal statutes. Document Analysts process requests from Inspectors to determine the authenticity of questioned or disputed documents. Analysts determine authenticity through the following procedures:

• Comparing "questioned" and "known" handwriting, typewriting, commercial printing, and other machine or mechanical impressions.
• Analyzing paper and ink.
• Restoring eradicated and obliterated impressions.
• Visualizing indented handwriting impressions.
• Detecting altered and counterfeit impressions.

Fingerprint Unit
The Fingerprint Unit provides technical assistance to Postal Inspectors who are investigating suspected violations of postal statutes by identifying suspects who have handled items of evidence. Latent Print Analysts are responsible for the following activities:

• Developing latent (invisible) prints on evidence.
• Comparing a latent print to a known fingerprint, palm print or footprint of suspects.
• Preparing charts demonstrating identifying features of "questioned" and "known" prints.
• Testifying in court to latent print identification.

The Fingerprint Unit interfaces with numerous automated fingerprint identification systems nationwide to assist in matching latent prints with local offenders.

Physical Sciences Unit
The Physical Sciences Unit, which includes a Physical Evidence and a Chemistry section, provides scientific support to the U.S. Postal Inspection Service offices nationwide. Analysts in this unit are engaged in a variety of functions, as follows:

• Conducting chemical analyses.
• Performing physical examinations and comparisons.
• Providing expert testimony in court.
• Processing crime scenes.
• Training Postal Inspectors.
• Interacting with other forensic science professionals.

Analysts in the Physical Evidence section conduct chemical analyses, examinations, and comparisons of these materials:

• Bomb debris and intact explosives.
• Firearms, tool marks, shoe, and tire impressions.
• Trace evidence such as adhesives, fibers, hair, paint, paper, plastic, rubber, and insulation from safes and tape.
• An accelerant from suspected arson fires.
• Serial number restorations.
• Tampered U.S. Postal Service equipment and mail.

The Chemistry section supports Postal Inspectors across the country by analyzing materials suspected of being controlled substances. Some of the more common controlled substances found in the mail include the following items:

• Cocaine
• Heroin
• LSD
• PCP
• Amphetamine
• Marijuana

Forensic Chemists conduct a variety of chemical analyses and testify to their findings in court, including the following:

• High-performance liquid chromatography (normal and reverse phase).
• Mass spectrophotometry (chemical impact and electron ionization).
• Gas chromatography.
• Four

Digital Evidence Unit
The Digital Evidence Unit has offices throughout the country. The unit is led by an Assistant Inspector in Charge located at the National Forensic Laboratory and is comprised of Inspector Program Managers, Forensic Computer Analysts and Ad Hoc analysts domiciled in each of the eighteen Inspection Service Field Divisions. In addition, there are Audio/Video Forensic Analysts located at the National Forensic Laboratory.

The Digital Evidence Unit is the principal group responsible for the collection, preservation, and examination of computer digital evidence in support of all Inspection Service investigations. Digital evidence analysts are tasked with examining computer evidence and any digital media for information or data pertinent to Postal Inspection Service investigations.

Computer evidence may include:

• Desktop computers
• Laptop computers
• Cellular phones
• MP3 devices
• Digital cameras and camcorders
• Personal digital assistant devices (PDAs)
• Any storage device that may hold digital media

In addition to processing cases, the Digital Evidence Unit is available for technical advice and assistance in seizing and preserving evidence at the crime scene.