Investigative Science

INSIDE THE HEAVILY GUARDED Marine Corps Base in Quantico, Va., sits the Federal Bureau of Investigation Laboratory. Each year, this facility processes thousands of pieces of forensic evidence in an effort to protect the U.S. from domestic and foreign threats.

"The FBI Laboratory is one of the leading forensic laboratories in the world," says Joseph A. DiZinno, retired director of the laboratory and now technical director of homeland security and law enforcement at BAE Systems.

The lab's primary role is to evaluate evidence collected during federal crime investigations, but it also serves state and local law enforcement organizations as well as international agencies and partners.

Depending on the nature of the evidence collected by field investigators, it may be examined by several different units within the lab, whose scientists wield state-of-the-art instrumentation and techniques to extract information about suspects, witnesses, victims, or a crime scene. The results are "part of a mosaic" that investigators piece together for every case, says David C. (Chris) Hassell, director of the FBI Laboratory.

An important component of the lab is its Chemistry Unit. Although a number of other groups, such as Explosives and DNA Units, handle chemistry-related work, the Chemistry Unit is the go-to group for all other molecule-centric evaluations.

With a 23-member staff, the Chemistry Unit includes chemists, metallurgists, forensic examiners, and instrument specialists who help investigators, for example, identify crime-scene materials such as powders, liquids, metals, paints, tapes, and polymers and who screen biological samples for drugs and poisons.

"We are looking for pretty much any chemical," says Marc A. LeBeau, chief of the FBI Laboratory's Chemistry Unit.

This task is rarely as easy as it is portrayed on popular forensics television dramas such as "CSI," the FBI scientists point out. For one thing, unlike the TV shows, in which all the work is done by one person in one lab, the Chemistry Unit is one of five units that make up the Scientific Analysis Section at the lab. The Chemistry Unit itself is divided into five subunits: General Chemistry, Metallurgy, Paints & Polymers, Toxicology, and Instrument Operation & Support.

All unknown solids, liquids, and other specimens that come into the unit are analyzed by the General Chemistry Subunit. Whatever it is, LeBeau says, the subunit will analyze it and characterize or identify it. For example, if the scientists are given a powderlike material, "We cannot tell if it is a McCormick spice mix, but we can say it is a food product" and not a drug, he notes. The inability to pinpoint the exact consumer product is a common problem associated with forensic analysis.

This subunit uses traditional chemical identification techniques including infrared spectrometry, gas chromatography/mass spectrometry, and liquid chromatography/MS to analyze evidence. These are high-end instruments that can push the analytical envelope; they tend to have higher sensitivity and increased throughput capabilities compared with instruments available at other forensic laboratories. "The instruments are what set this lab apart from other forensics facilities," LeBeau notes.

LeBeau is particularly proud of the Chemistry Unit's direct analysis in real-time time-of-flight MS, which can identify solid or liquid samples, such as cocaine, in a matter of seconds. The FBI discovered this "CSI"-like instrument a couple of years ago at the analytical chemistry conference Pittcon. It allows quick identification of materials, which can then be verified by other techniques.

MS INSTRUMENTATION is also important to the unit's Toxicology Subunit. It allows FBI toxicologists to identify drugs that could be used as poisons or incapacitating agents. Criminals often use these types of drugs, including Benadryl and the date-rape drug flunitrazepam, to carry out murders and sexual assaults.

In cases involving drug-facilitated sexual assaults in which a victim may not report the incident right away, the power of instrumentation really shows itself, LeBeau says. For example, FBI analysts can often determine whether a drug may have been used in a crime that occurred days, weeks, or months before evidence is collected by detecting trace levels of the drug's metabolites in urine, hair, and other specimens, he notes.

Analysts in the Toxicology Subunit also spend part of their time improving their techniques. For instance, by developing automated extraction processes that are directly linked to the analytical instruments, the subunit has increased the number of samples it can analyze in a day.

The subunit is also adding to the portfolio of chemicals that it can detect in its toxicology screens. Specifically, it is developing and validating methods for detecting metabolites of chemical warfare agents. One goal is to develop a protocol to identify nerve agent metabolites in case such agents are used in a terrorist attack, according to LeBeau.

The Metallurgy Subunit can also play a role in solving crimes and developing evidence left behind in acts of terrorism. This subunit has analyzed metallic materials recovered from bombings around the world. It is often able to determine the manufacturer of an item, LeBeau tells C&EN. This information helps investigators determine the possible origin of the metallic materials used in improvised explosive devices, which may help identify the responsible parties.

In addition to compositional analysis of metals used in terrorist attacks and other crimes, the Metallurgy Subunit also conducts failure analysis. An example of this type of analysis includes determining whether a broken car light was on during a collision, which may be useful, say, in investigating fatal vehicle accidents.

"This group is the only full-service lab in the U.S. that does metallurgy as a full-time discipline," LeBeau says. For this reason, the subunit's services are utilized quite frequently by those outside the FBI, he adds.

Similar to how metallurgists can help determine the origin of metal pieces recovered from a crime scene, the Paints & Polymers Subunit can use the results of their examinations of automobile paint chips to identify potential sources.

This subunit of the Chemistry Unit has access to a number of resources including the National Automotive Paint File and the Paint Data Query. NAPF is maintained by the FBI Laboratory and includes color coat samples of makes and models of vehicles sold for personal use in North America. PDQ was developed in conjunction with the Royal Canadian Mounted Police and provides additional information about the other layers of the paint, such as the primer and clear coat. Such information can help identify the assembly plant from which a vehicle originated.

A TYPICAL automobile paint-chip analysis includes a "combination of infrared spectroscopy, microscopy, pyrolysis gas chromatography/MS, and scanning electron microscope energy-dispersive X-ray spectroscopy," LeBeau says. Data from the examination can lead to the identification of the make, model, and year of the vehicle as well as potential vehicle identification numbers for the type of vehicle that may have been involved.

The Paints & Polymers Subunit also maintains a database of compositions of a wide variety of tape including duct and electrical tapes. "You can use duct tape for everything—and criminals do," LeBeau notes. Criminals often use tape to bind and gag victims and to construct improvised explosive devices, LeBeau says.

The Chemistry Unit analyzes the tapes' adhesive layer and backing. Knowing the composition of tape found at a crime scene helps investigators determine the manufacturing, distribution, and potential sales locations of that tape, all of which can help catch a perpetrator, he explains.

Many of the analyses conducted by the Chemistry Unit do not necessarily provide stand-alone evidence, LeBeau acknowledges. But "in every case we are either helping put the bad guy in jail or we are showing that someone is innocent."